Adding iree_hal_amdgpu_system_t to manage HSA/topology/pools. (iree-org#21043)

The system is shared across all physical devices within a logical device
and owns resources shared across them (it's how we avoid a cycle between
logical<->physical device impls).

Author: benvanik

runtime/src/iree/hal/drivers/amdgpu/BUILD.bazel

@@ -46,8 +46,8 @@ iree_runtime_cc_library(
         # "semaphore.h",
         # "semaphore_pool.c",
         # "semaphore_pool.h",
-        # "system.c",
-        # "system.h",
+        "system.c",
+        "system.h",
         # "trace_buffer.c",
         # "trace_buffer.h",
     ],

runtime/src/iree/hal/drivers/amdgpu/CMakeLists.txt

@@ -30,6 +30,8 @@ iree_cc_library(
     "logical_device.h"
     "physical_device.c"
     "physical_device.h"
+    "system.c"
+    "system.h"
   DEPS
     iree::base
     iree::base::internal