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/e9a02650d3b34c7d863ac64b89a8b9bf180f4696/src/spec/doc/core-async-await.adoc
2. https://github.com/apache/groovy/actions/runs/22549038929/artifacts/5711485468

[codecov-commenter]

Codecov Report

❌ Patch coverage is 78.91269% with 128 lines in your changes missing coverage. Please review.
✅ Project coverage is 66.8503%. Comparing base (a0feded) to head (59f9620).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
.../org/apache/groovy/runtime/async/AsyncSupport.java	73.1844%	35 Missing and 13 partials ⚠️
...va/groovy/concurrent/AwaitableAdapterRegistry.java	69.0909%	28 Missing and 6 partials ⚠️
...ehaus/groovy/transform/AsyncASTTransformation.java	79.7980%	10 Missing and 10 partials ⚠️
...che/groovy/runtime/async/AsyncStreamGenerator.java	58.8235%	13 Missing and 1 partial ⚠️
...odehaus/groovy/transform/AsyncTransformHelper.java	90.3846%	0 Missing and 5 partials ⚠️
src/main/java/groovy/concurrent/AsyncUtils.java	78.9474%	4 Missing ⚠️
src/main/java/groovy/concurrent/AsyncStream.java	75.0000%	1 Missing ⚠️
.../main/java/groovy/concurrent/AwaitableAdapter.java	50.0000%	1 Missing ⚠️
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	98.5075%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2387        +/-   ##
==================================================
+ Coverage     66.7519%   66.8503%   +0.0984%     
- Complexity      29846      30082       +236     
==================================================
  Files            1382       1393        +11     
  Lines          116130     116897       +767     
  Branches        20475      20629       +154     
==================================================
+ Hits            77519      78146       +627     
- Misses          32278      32386       +108     
- Partials         6333       6365        +32     

Files with missing lines	Coverage Δ
src/main/java/groovy/concurrent/AwaitResult.java	100.0000% <100.0000%> (ø)
src/main/java/groovy/concurrent/Awaitable.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%)	⬆️
src/main/java/groovy/concurrent/AsyncStream.java	75.0000% <75.0000%> (ø)
.../main/java/groovy/concurrent/AwaitableAdapter.java	50.0000% <50.0000%> (ø)
...va/org/apache/groovy/parser/antlr4/AstBuilder.java	86.8156% <98.5075%> (+0.3535%)	⬆️
src/main/java/groovy/concurrent/AsyncUtils.java	78.9474% <78.9474%> (ø)
...odehaus/groovy/transform/AsyncTransformHelper.java	90.3846% <90.3846%> (ø)
...che/groovy/runtime/async/AsyncStreamGenerator.java	58.8235% <58.8235%> (ø)
... and 3 more

... and 10 files with indirect coverage changes

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