Avoid allocation for positional splat for literal array keyword argument

If all nodes in the array are safe, then it is safe to avoid
allocation for the positional splat:

```ruby
m(*a, kw: [:a])   # Safe
m(*a, kw: [meth]) # Unsafe
```

This avoids an unnecessary allocation in a Rails method call.
Details: https://github.com/rails/rails/pull/54949/files#r2052645431

Author: jeremyevans

compile.c

@@ -6643,6 +6643,14 @@ setup_args_dup_rest_p(const NODE *argn)
         return false;
       case NODE_COLON2:
         return setup_args_dup_rest_p(RNODE_COLON2(argn)->nd_head);
+      case NODE_LIST:
+        while (argn) {
+            if (setup_args_dup_rest_p(RNODE_LIST(argn)->nd_head)) {
+                return true;
+            }
+            argn = RNODE_LIST(argn)->nd_next;
+        }
+        return false;
       default:
         return true;
     }

prism_compile.c

@@ -1882,6 +1882,15 @@ pm_setup_args_dup_rest_p(const pm_node_t *node)
       }
       case PM_IMPLICIT_NODE:
         return pm_setup_args_dup_rest_p(((const pm_implicit_node_t *) node)->value);
+      case PM_ARRAY_NODE: {
+        const pm_array_node_t *cast = (const pm_array_node_t *) node;
+        for (size_t index = 0; index < cast->elements.size; index++) {
+            if (pm_setup_args_dup_rest_p(cast->elements.nodes[index])) {
+                return true;
+            }
+        }
+        return false;
+      }
       default:
         return true;
     }

test/ruby/test_allocation.rb

@@ -807,6 +807,13 @@ def self.Object; Object end
         check_allocations(0, 1, "keyword(*empty_array, a: ->{}#{block})") # LAMBDA
         check_allocations(0, 1, "keyword(*empty_array, a: $1#{block})") # NTH_REF
         check_allocations(0, 1, "keyword(*empty_array, a: $`#{block})") # BACK_REF
+
+        # LIST: Only 1 array (literal [:c]), not 2 (one for [:c] and one for *empty_array)
+        check_allocations(1, 1, "keyword(*empty_array, a: empty_array, b: [:c]#{block})")
+        check_allocations(1, 1, "keyword(*empty_array, a: empty_array, b: [:c, $x]#{block})")
+        # LIST unsafe: 2 (one for [Object()] and one for *empty_array)
+        check_allocations(2, 1, "keyword(*empty_array, a: empty_array, b: [Object()]#{block})")
+        check_allocations(2, 1, "keyword(*empty_array, a: empty_array, b: [:c, $x, Object()]#{block})")
       RUBY
     end
 
@@ -877,6 +884,13 @@ def self.Object; Object end
         check_allocations(0, 1, "keyword.(*empty_array, a: ->{}#{block})") # LAMBDA
         check_allocations(0, 1, "keyword.(*empty_array, a: $1#{block})") # NTH_REF
         check_allocations(0, 1, "keyword.(*empty_array, a: $`#{block})") # BACK_REF
+
+        # LIST safe: Only 1 array (literal [:c]), not 2 (one for [:c] and one for *empty_array)
+        check_allocations(1, 1, "keyword.(*empty_array, a: empty_array, b: [:c]#{block})")
+        check_allocations(1, 1, "keyword.(*empty_array, a: empty_array, b: [:c, $x]#{block})")
+        # LIST unsafe: 2 (one for [:c] and one for *empty_array)
+        check_allocations(2, 1, "keyword.(*empty_array, a: empty_array, b: [Object()]#{block})")
+        check_allocations(2, 1, "keyword.(*empty_array, a: empty_array, b: [:c, $x, Object()]#{block})")
       RUBY
     end