Revert "[vm] Enable new implementation of async/async* in JIT mode"

This reverts commit b3544c4.

Reason for revert: avoid incompatibility between Dart->kernel compiler
and Dart VM during Dart and Flutter rolls (b/234850964).

TEST=ci

Original change's description:
> [vm] Enable new implementation of async/async* in JIT mode
>
> TEST=ci
>
> Issue: #48378
> Change-Id: I0fc069508cb1ce5648deb6604171dfdcd5bcb5c8
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/246082
> Reviewed-by: Johnni Winther <johnniwinther@google.com>
> Reviewed-by: Martin Kustermann <kustermann@google.com>
> Reviewed-by: Slava Egorov <vegorov@google.com>
> Commit-Queue: Alexander Markov <alexmarkov@google.com>

TBR=vegorov@google.com,kustermann@google.com,rmacnak@google.com,alexmarkov@google.com,johnniwinther@google.com

Change-Id: I6157623857dbfa9bb07eb1f620d100f5b24314d9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Issue: #48378
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247243
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

pkg/frontend_server/lib/frontend_server.dart

@@ -58,7 +58,7 @@ ArgParser argParser = ArgParser(allowTrailingOptions: true)
           'supported when --aot and --minimal-kernel are not used.',
       defaultsTo: null)
   ..addFlag('compact-async',
-      help: 'Enable new compact async/await implementation.', defaultsTo: true)
+      help: 'Enable new compact async/await implementation.', defaultsTo: null)
   ..addFlag('tfa',
       help:
           'Enable global type flow analysis and related transformations in AOT mode.',
@@ -541,7 +541,7 @@ class FrontendCompiler implements CompilerInterface {
       nullSafety: compilerOptions.nnbdMode == NnbdMode.Strong,
       supportMirrors: options['support-mirrors'] ??
           !(options['aot'] || options['minimal-kernel']),
-      compactAsync: options['compact-async'],
+      compactAsync: options['compact-async'] ?? options['aot'],
     );
     if (compilerOptions.target == null) {
       print('Failed to create front-end target ${options['target']}.');

pkg/kernel/lib/target/targets.dart

@@ -22,7 +22,7 @@ class TargetFlags {
       {this.trackWidgetCreation = false,
       this.enableNullSafety = false,
       this.supportMirrors = true,
-      this.compactAsync = true});
+      this.compactAsync = false});
 
   @override
   bool operator ==(other) {
@@ -786,7 +786,8 @@ class TestTargetFlags extends TargetFlags {
       this.unsupportedDartLibraries: const {}})
       : super(
             trackWidgetCreation: trackWidgetCreation,
-            enableNullSafety: enableNullSafety);
+            enableNullSafety: enableNullSafety,
+            compactAsync: true);
 }
 
 mixin TestTargetMixin on Target {

pkg/vm/lib/kernel_front_end.dart

@@ -81,7 +81,7 @@ void declareCompilerOptions(ArgParser args) {
           'supported when --aot and --minimal-kernel are not used.',
       defaultsTo: null);
   args.addFlag('compact-async',
-      help: 'Enable new compact async/await implementation.', defaultsTo: true);
+      help: 'Enable new compact async/await implementation.', defaultsTo: null);
   args.addOption('depfile', help: 'Path to output Ninja depfile');
   args.addOption('from-dill',
       help: 'Read existing dill file instead of compiling from sources',
@@ -202,7 +202,7 @@ Future<int> runCompiler(ArgResults options, String usage) async {
   final String? manifestFilename = options['manifest'];
   final String? dataDir = options['component-name'] ?? options['data-dir'];
   final bool? supportMirrors = options['support-mirrors'];
-  final bool compactAsync = options['compact-async'];
+  final bool compactAsync = options['compact-async'] ?? aot;
 
   final bool minimalKernel = options['minimal-kernel'];
   final bool treeShakeWriteOnlyFields = options['tree-shake-write-only-fields'];
@@ -617,7 +617,7 @@ Target? createFrontEndTarget(String targetName,
     {bool trackWidgetCreation = false,
     bool nullSafety = false,
     bool supportMirrors = true,
-    bool compactAsync = true}) {
+    bool compactAsync = false}) {
   // Make sure VM-specific targets are available.
   installAdditionalTargets();