refactor: do not specify g_direct_{hash, equal} for performance

g_hash_table_new/g_hash_table_new_full:

```
 * Hash values returned by @hash_func are used to determine where keys
 * are stored within the #GHashTable data structure. The g_direct_hash(),
 * g_int_hash(), g_int64_hash(), g_double_hash() and g_str_hash()
 * functions are provided for some common types of keys.
 * If @hash_func is %NULL, g_direct_hash() is used.
 *
 * @key_equal_func is used when looking up keys in the #GHashTable.
 * The g_direct_equal(), g_int_equal(), g_int64_equal(), g_double_equal()
 * and g_str_equal() functions are provided for the most common types
 * of keys. If @key_equal_func is %NULL, keys are compared directly in
 * a similar fashion to g_direct_equal(), but without the overhead of
 * a function call. @key_equal_func is called with the key from the hash table
 * as its first parameter, and the user-provided key to check against as
 * its second.
```

1. `If @hash_func is %NULL, g_direct_hash() is used.`
so passing this argument to the function is unnecessary.
2. `If @key_equal_func is %NULL, keys are compared directly in a similar fashion to g_direct_equal(), but without the overhead of a function call.`
so passing g_direct_equal instead of NULL will make the lookups slower.

mechanical change using the following commands:
```sh
sed -i '' 's/g_direct_hash/NULL/g' ./hw/**/*.c ./util/**/*.c ./target/**/*.c ./accel/**/*.c ./system/**/*.c ./migration/**/*.c
sed -i '' 's/g_direct_equal/NULL/g' ./hw/**/*.c ./util/**/*.c ./target/**/*.c ./accel/**/*.c ./system/**/*.c ./migration/**/*.c
```

Author: VisualEhrmanntraut

accel/kvm/kvm-all.c

@@ -2458,7 +2458,7 @@ static void kvm_irqchip_create(KVMState *s)
 
     kvm_init_irq_routing(s);
 
-    s->gsimap = g_hash_table_new(g_direct_hash, g_direct_equal);
+    s->gsimap = g_hash_table_new(NULL, NULL);
 }
 
 /* Find number of supported CPUs using the recommended

hw/arm/apple-silicon/dart.c

@@ -653,8 +653,7 @@ static void apple_dart_reset(DeviceState *dev)
             if (mapper->tlb) {
                 g_hash_table_destroy(mapper->tlb);
             }
-            mapper->tlb = g_hash_table_new_full(g_direct_hash, g_direct_equal,
-                                                NULL, g_free);
+            mapper->tlb = g_hash_table_new_full(NULL, NULL, NULL, g_free);
             break;
         }
         default:

hw/i386/kvm/xen_gnttab.c

@@ -498,7 +498,7 @@ static struct xengntdev_handle *xen_be_gnttab_open(void)
 {
     struct xengntdev_handle *xgt = g_new0(struct xengntdev_handle, 1);
 
-    xgt->active_maps = g_hash_table_new(g_direct_hash, g_direct_equal);
+    xgt->active_maps = g_hash_table_new(NULL, NULL);
     return xgt;
 }
 

hw/i386/kvm/xenstore_impl.c

@@ -1374,7 +1374,7 @@ XenstoreImplState *xs_impl_create(unsigned int dom_id)
     GList *perms;
 
     s->watches = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, NULL);
-    s->transactions = g_hash_table_new_full(g_direct_hash, g_direct_equal,
+    s->transactions = g_hash_table_new_full(NULL, NULL,
                                             NULL, xs_tx_free);
 
     perms = g_list_append(NULL, xs_perm_as_string(XS_PERM_NONE, 0));

hw/misc/apple-silicon/a7iop/rtkit.c

@@ -441,8 +441,7 @@ void apple_rtkit_init(AppleRTKit *s, void *opaque, const char *role,
                      apple_rtkit_handle_messages_bh);
 
     s->opaque = opaque ? opaque : s;
-    s->endpoints =
-        g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL, g_free);
+    s->endpoints = g_hash_table_new_full(NULL, NULL, NULL, g_free);
     s->ops = ops;
     QTAILQ_INIT(&s->rollcall);
     qemu_mutex_init(&s->lock);

hw/ppc/vof.c

@@ -1003,7 +1003,7 @@ void vof_init(Vof *vof, uint64_t top_addr, Error **errp)
 {
     vof_cleanup(vof);
 
-    vof->of_instances = g_hash_table_new_full(g_direct_hash, g_direct_equal,
+    vof->of_instances = g_hash_table_new_full(NULL, NULL,
                                               NULL, vof_instance_free);
     vof->claimed = g_array_new(false, false, sizeof(OfClaimed));
 

hw/riscv/riscv-iommu.c

@@ -2583,7 +2583,7 @@ static void riscv_iommu_realize(DeviceState *dev, Error **errp)
     if (s->cap & RISCV_IOMMU_CAP_HPM) {
         s->hpm_timer =
             timer_new_ns(QEMU_CLOCK_VIRTUAL, riscv_iommu_hpm_timer_cb, s);
-        s->hpm_event_ctr_map = g_hash_table_new(g_direct_hash, g_direct_equal);
+        s->hpm_event_ctr_map = g_hash_table_new(NULL, NULL);
     }
 }
 

migration/postcopy-ram.c

@@ -269,7 +269,7 @@ static GHashTable *blocktime_init_tid_to_vcpu_hash(void)
      * be 0, which means NULL.  Then when lookup we can never know whether
      * it's 0 or "not found".  Hence use an indirection for CPU index.
      */
-    GHashTable *table = g_hash_table_new_full(g_direct_hash, g_direct_equal,
+    GHashTable *table = g_hash_table_new_full(NULL, NULL,
                                               NULL, g_free);
     CPUState *cpu;
 
@@ -311,8 +311,8 @@ static struct PostcopyBlocktimeContext *blocktime_context_new(void)
      *
      * The value will be a list of BlocktimeVCPUEntry entries.
      */
-    ctx->vcpu_addr_hash = g_hash_table_new_full(g_direct_hash,
-                                                g_direct_equal,
+    ctx->vcpu_addr_hash = g_hash_table_new_full(NULL,
+                                                NULL,
                                                 NULL,
                                                 blocktime_vcpu_list_free);
 

migration/rdma.c

@@ -2309,7 +2309,7 @@ static int qemu_rdma_source_init(RDMAContext *rdma, bool pin_all, Error **errp)
     qemu_rdma_init_ram_blocks(rdma);
 
     /* Build the hash that maps from offset to RAMBlock */
-    rdma->blockmap = g_hash_table_new(g_direct_hash, g_direct_equal);
+    rdma->blockmap = g_hash_table_new(NULL, NULL);
     for (int i = 0; i < rdma->local_ram_blocks.nb_blocks; i++) {
         g_hash_table_insert(rdma->blockmap,
                 (void *)(uintptr_t)rdma->local_ram_blocks.block[i].offset,

system/memory.c

@@ -1043,7 +1043,7 @@ static void flatviews_init(void)
         return;
     }
 
-    flat_views = g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL,
+    flat_views = g_hash_table_new_full(NULL, NULL, NULL,
                                        (GDestroyNotify) flatview_unref);
     if (!empty_view) {
         empty_view = generate_memory_topology(NULL);
@@ -3563,7 +3563,7 @@ static void mtree_info_flatview(bool dispatch_tree, bool owner)
     AddressSpace *as;
     FlatView *view;
     GArray *fv_address_spaces;
-    GHashTable *views = g_hash_table_new(g_direct_hash, g_direct_equal);
+    GHashTable *views = g_hash_table_new(NULL, NULL);
     AccelClass *ac = ACCEL_GET_CLASS(current_accel());
 
     if (ac->has_memory) {
@@ -3639,7 +3639,7 @@ static void mtree_info_as(bool dispatch_tree, bool owner, bool disabled)
     MemoryRegionListHead ml_head;
     MemoryRegionList *ml, *ml2;
     AddressSpace *as;
-    GHashTable *views = g_hash_table_new(g_direct_hash, g_direct_equal);
+    GHashTable *views = g_hash_table_new(NULL, NULL);
     GSList *as_same_root_mr_list;
     struct AddressSpaceInfo asi = {
         .ml_head = &ml_head,