[objective_c] Rename gc_safepoint_test → protocol_builder_test, remove redundant object test

The 'protocol object survives GC after build' test kept failing on CI (ARM64)
because doGC() is inlinable — after inlining, the optimizer dropped ref from
the GC root set before the GC trigger, causing a spurious retain-count-0.
The test didn't cover the issue #3209 fix; general ObjCObjectRef lifecycle is
already covered by autorelease_test, nsarray_test, nsset_test, nsdictionary_test,
ns_input_stream_test, and observer_test.

Renamed to protocol_builder_test.dart to match the <feature>_test.dart convention.

Author: Henawey

…/objective_c/test/gc_safepoint_test.dart …ective_c/test/protocol_builder_test.dartpkgs/objective_c/test/gc_safepoint_test.dart renamed to pkgs/objective_c/test/protocol_builder_test.dart pkgs/objective_c/test/gc_safepoint_test.dart renamed to pkgs/objective_c/test/protocol_builder_test.dart

@@ -13,26 +13,6 @@ import 'package:test/test.dart';
 
 import 'util.dart';
 
-// Checks that a protocol object built by ObjCProtocolBuilder.build() retains a
-// positive retain count after GC. Intentionally never-inlined so the JIT
-// performs its own liveness analysis on a proper synchronous stack frame.
-// In an async state machine, Finalizable liveness across await points is
-// unreliable: variables not referenced after a suspension point may be dropped
-// from the GC root set, causing premature release on aggressively-optimising
-// platforms (e.g. ARM64 CI).
-@pragma('vm:never-inline')
-bool _buildAndCheckProtocolObject() {
-  final builder = ObjCProtocolBuilder();
-  final obj = builder.build(keepIsolateAlive: false);
-  // ObjCObjectRef is Finalizable. Because this function is never-inlined, the
-  // JIT tracks ref in the GC stack map throughout the frame — including across
-  // the non-leaf FFI safepoints inside doGC() and objectRetainCount().
-  final ref = obj.ref;
-  final raw = ref.pointer;
-  doGC();
-  return objectRetainCount(raw) > 0;
-}
-
 // Directly exercises the blockRef extraction pattern from the production fix.
 // Extract block.ref into a local `blockRef` (static type ObjCBlockRef, which
 // transitively implements Finalizable). The Finalizable contract keeps blockRef
@@ -55,18 +35,6 @@ bool _gcAndCheckBlock() {
 }
 
 void main() {
-  group('object model', () {
-    test('protocol object survives GC after build', () {
-      if (!canDoGC) {
-        markTestSkipped(
-          'Dart_ExecuteInternalCommand unavailable — gc-now is a no-op.',
-        );
-        return;
-      }
-      expect(_buildAndCheckProtocolObject(), isTrue);
-    });
-  });
-
   group('block wrapper not freed at GC safepoints', () {
     setUpAll(() {
       initGCInject();