GROOVY-9381: Support async/await like ES7

[daniellansun]

https://issues.apache.org/jira/browse/GROOVY-9381

See also:

1. https://github.com/apache/groovy/blob/GROOVY-9381_3/src/spec/doc/core-async-await.adoc
2. https://github.com/apache/groovy/actions/runs/22797807155/artifacts/5810903230

[codecov-commenter]

Codecov Report

❌ Patch coverage is 90.82840% with 62 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.9041%. Comparing base (7d8349c) to head (90466c2).

Files with missing lines	Patch %	Lines
.../org/apache/groovy/runtime/async/AsyncSupport.java	90.2128%	13 Missing and 10 partials ⚠️
...ehaus/groovy/transform/AsyncASTTransformation.java	80.2083%	8 Missing and 11 partials ⚠️
...va/groovy/concurrent/AwaitableAdapterRegistry.java	90.5983%	4 Missing and 7 partials ⚠️
...odehaus/groovy/transform/AsyncTransformHelper.java	92.4242%	1 Missing and 4 partials ⚠️
...che/groovy/runtime/async/AsyncStreamGenerator.java	92.5000%	1 Missing and 2 partials ⚠️
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	98.4848%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2387        +/-   ##
==================================================
+ Coverage     66.7571%   66.9041%   +0.1470%     
- Complexity      29856      30081       +225     
==================================================
  Files            1382       1392        +10     
  Lines          116130     116806       +676     
  Branches        20471      20581       +110     
==================================================
+ Hits            77525      78148       +623     
- Misses          32275      32296        +21     
- Partials         6330       6362        +32     

Files with missing lines	Coverage Δ
src/main/java/groovy/concurrent/AsyncStream.java	100.0000% <100.0000%> (ø)
src/main/java/groovy/concurrent/AwaitResult.java	100.0000% <100.0000%> (ø)
src/main/java/groovy/concurrent/Awaitable.java	100.0000% <100.0000%> (ø)
.../main/java/groovy/concurrent/AwaitableAdapter.java	100.0000% <100.0000%> (ø)
...org/apache/groovy/runtime/async/GroovyPromise.java	100.0000% <100.0000%> (ø)
...ain/java/org/codehaus/groovy/ast/ModifierNode.java	77.7778% <100.0000%> (+0.4193%)	⬆️
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	86.8536% <98.4848%> (+0.3464%)	⬆️
...che/groovy/runtime/async/AsyncStreamGenerator.java	92.5000% <92.5000%> (ø)
...odehaus/groovy/transform/AsyncTransformHelper.java	92.4242% <92.4242%> (ø)
...va/groovy/concurrent/AwaitableAdapterRegistry.java	90.5983% <90.5983%> (ø)
... and 2 more

... and 4 files with indirect coverage changes

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