Failures on [vm/concurrency/debugger] Fix pool patching synchronization for lightweight isolates breakpoints.

[aam]

The tests

vm/dart_2/isolates/reload_many_isolates_live_and_die_test Timeout (expected Pass)

is failing on configurations

dartk-win-release-x64

--- Command "vm" (took 04:00.000015s):
set DART_CONFIGURATION=ReleaseX64 & set DART_SUPPRESS_WER=1 & set DART_CRASHPAD_HANDLER=C:\b\s\w\ir\out\ReleaseX64\crashpad_handler.exe & out\ReleaseX64\dart.exe --ignore-unrecognized-flags --packages=C:\b\s\w\ir\.packages C:\b\s\w\ir\runtime\tests\vm\dart_2\isolates\reload_many_isolates_live_and_die_test.dart

exit code:
null

diagnostics:
win_sdk_path not found

stdout:
Launching out\ReleaseX64\dart.exe --packages=.packages --snapshot-kind=kernel --snapshot=C:\b\s\w\itu485us\39358070\test.dart.0.dill C:\b\s\w\itu485us\39358070\test.dart
stdout: Info: Compiling with sound null safety
Launching out\ReleaseX64\dart.exe --packages=.packages --snapshot-kind=kernel --snapshot=C:\b\s\w\itu485us\39358070\test.dart.1.dill C:\b\s\w\itu485us\39358070\test.dart
stdout: Info: Compiling with sound null safety
Launching out\ReleaseX64\dart.exe --enable-vm-service:0 --disable-dart-dev --disable-service-auth-codes --enable-isolate-groups --experimental-enable-isolate-groups-jit file:///C:/b/s/w/itu485us/39358070/test.dart.0.dill
stdout: Observatory listening on http://127.0.0.1:49978/

--- Re-run this test:
python tools/test.py -n dartk-win-release-x64 vm/dart_2/isolates/reload_many_isolates_live_and_die_test

[aam]

thread 1 IsolateGroup::ForEachIsolate attempts to grab isolates_lock inside of RunningWithStoppedMutators and gets deadlocked as another thread is stuck on exiting the safepoint after acquiring that lock.

thread 1

 	dart.exe!dart::Monitor::Wait(__int64 millis) Line 350	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::MonitorLocker::Wait(__int64 millis) Line 173	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::SafepointRwLock::TryEnterRead(bool can_block, bool *) Line 132	C++	Symbols loaded.
 	dart.exe!dart::SafepointRwLock::EnterRead() Line 117	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::SafepointReadRwLocker::SafepointReadRwLocker(dart::ThreadState * thread_state, dart::SafepointRwLock * rw_lock) Line 416	C++	Symbols loaded.
 	dart.exe!dart::IsolateGroup::ForEachIsolate(std::function<void (dart::Isolate *)> function, bool at_safepoint) Line 2744	C++	Symbols loaded.
>	[Inline Frame] dart.exe!dart::CompileParsedFunctionHelper::Compile::<unnamed-tag>::operator()() Line 615	C++	Symbols loaded.
 	dart.exe!dart::LambdaCallable<`lambda at ../../runtime/vm/compiler/jit/compiler.cc:603:33'>::Call() Line 130	C++	Symbols loaded.
 	dart.exe!dart::IsolateGroup::RunWithStoppedMutatorsCallable(dart::Callable * single_current_mutator, dart::Callable * otherwise, bool use_force_growth_in_otherwise) Line 2791	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::IsolateGroup::RunWithStoppedMutators(dart::CompileParsedFunctionHelper::Compile::<unnamed-tag> function, bool use_force_growth) Line 659	C++	Symbols loaded.
 	dart.exe!dart::CompileParsedFunctionHelper::Compile(dart::CompilationPipeline * pipeline) Line 645	C++	Symbols loaded.
 	dart.exe!dart::CompileFunctionHelper(dart::CompilationPipeline * pipeline, const dart::Function & function, volatile bool optimized, __int64 osr_id) Line 730	C++	Symbols loaded.
 	dart.exe!dart::Compiler::CompileFunction(dart::Thread * thread, const dart::Function & function) Line 860	C++	Symbols loaded.
 	dart.exe!dart::Function::EnsureHasCode() Line 9721	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::DRT_HelperCompileFunction(dart::Isolate * isolate, dart::Thread * thread, dart::Zone * zone, dart::NativeArguments arguments) Line 231	C++	Symbols loaded.
 	dart.exe!dart::DRT_CompileFunction(dart::NativeArguments arguments) Line 211	C++	Symbols loaded.

thread 2:

 	dart.exe!dart::Monitor::Wait(__int64 millis) Line 350	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::MonitorLocker::Wait(__int64 millis) Line 173	C++	Symbols loaded.
 	dart.exe!dart::SafepointHandler::ExitSafepointUsingLock(dart::Thread * T) Line 221	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::Thread::ExitSafepoint() Line 847	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::TransitionVMToBlocked::~TransitionVMToBlocked() Line 246	C++	Symbols loaded.
 	dart.exe!dart::SafepointRwLock::EnterWrite() Line 176	C++	Symbols loaded.
 	[Inline Frame] dart.exe!dart::SafepointWriteRwLocker::SafepointWriteRwLocker(dart::ThreadState * thread_state, dart::SafepointRwLock * rw_lock) Line 463	C++	Symbols loaded.
>	[Inline Frame] dart.exe!dart::IsolateGroup::UnregisterIsolate(dart::Isolate * isolate) Line 466	C++	Symbols loaded.
 	dart.exe!dart::Isolate::LowLevelCleanup(dart::Isolate * isolate) Line 2548	C++	Symbols loaded.
 	dart.exe!dart::Isolate::Shutdown() Line 2528	C++	Symbols loaded.
 	dart.exe!Dart_ShutdownIsolate() Line 1483	C++	Symbols loaded.
 	dart.exe!dart::MessageHandler::TaskCallback() Line 511	C++	Symbols loaded.
 	dart.exe!dart::ThreadPool::WorkerLoop(dart::ThreadPool::Worker * worker) Line 160	C++	Symbols loaded.
 	dart.exe!dart::ThreadPool::Worker::Main(unsigned __int64 args) Line 325	C++	Symbols loaded.
 	dart.exe!dart::ThreadEntry(void * data_ptr) Line 79	C++	Symbols loaded.
 	dart.exe!thread_start<unsigned int (__cdecl*)(void *),1>(void * const parameter) Line 97	C++	Symbols loaded.