src: force gc for flaky (deadlock) tests

This patch adds a new flag `force_gc_for_test` (internal use for test
purpose only) to force GC specifically for flaky tests that suffer from
deadlock.

The deadlock occurs when:
1. Main thread calls DrainTasks and executes worker tasks
2. Worker task needs memory allocation requiring GC
3. GC must run on main thread, but main thread is busy running the
   worker task

Author: jakecastelli

Diff for: src/node_options.cc

@@ -1166,6 +1166,10 @@ PerProcessOptionsParser::PerProcessOptionsParser(
             "force FIPS crypto (cannot be disabled)",
             &PerProcessOptions::force_fips_crypto,
             kAllowedInEnvvar);
+  AddOption("--force-gc-for-test",
+            "",
+            &PerProcessOptions::force_gc_for_test,
+            kAllowedInEnvvar);
   AddOption("--secure-heap",
             "total size of the OpenSSL secure heap",
             &PerProcessOptions::secure_heap,

Diff for: src/node_options.h

@@ -321,6 +321,7 @@ class PerProcessOptions : public Options {
   std::string snapshot_blob;
 
   std::vector<std::string> security_reverts;
+  bool force_gc_for_test = false;
   bool print_bash_completion = false;
   bool print_help = false;
   bool print_v8_help = false;

Diff for: src/node_platform.cc

@@ -463,9 +463,16 @@ void NodePlatform::DrainTasks(Isolate* isolate) {
   std::shared_ptr<PerIsolatePlatformData> per_isolate = ForNodeIsolate(isolate);
   if (!per_isolate) return;
 
+
   do {
+    if (per_process::cli_options->force_gc_for_test) {
+      isolate->RequestGarbageCollectionForTesting(
+          Isolate::GarbageCollectionType::kFullGarbageCollection);
+    }
+
     // Worker tasks aren't associated with an Isolate.
     worker_thread_task_runner_->BlockingDrain();
+
   } while (per_isolate->FlushForegroundTasksInternal());
 }