GROOVY-11630: optimize void groovy method return in expression statement

[eric-milles]

consolidate metadata keys to shared value

[paulk-asert]

LGTM;

[codecov-commenter]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.9506%. Comparing base (840e57a) to head (31eb3d9).
⚠️ Report is 790 commits behind head on master.

Files with missing lines	Patch %	Lines
...codehaus/groovy/classgen/asm/InvocationWriter.java	0.0000%	0 Missing and 1 partial ⚠️
...groovy/classgen/asm/sc/StaticInvocationWriter.java	66.6667%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2203        +/-   ##
==================================================
+ Coverage     68.9489%   68.9506%   +0.0018%     
- Complexity      29562      29564         +2     
==================================================
  Files            1423       1423                
  Lines          113909     113909                
  Branches        19754      19754                
==================================================
+ Hits            78539      78541         +2     
+ Misses          28773      28770         -3     
- Partials         6597       6598         +1     

Files with missing lines	Coverage Δ
...rg/codehaus/groovy/classgen/AsmClassGenerator.java	85.1608% <ø> (ø)
...us/groovy/classgen/asm/BinaryExpressionHelper.java	89.1589% <100.0000%> (ø)
...ssgen/asm/BinaryExpressionMultiTypeDispatcher.java	88.8325% <100.0000%> (ø)
.../codehaus/groovy/classgen/asm/StatementWriter.java	96.9613% <100.0000%> (-0.0167%)	⬇️
...taticTypesBinaryExpressionMultiTypeDispatcher.java	78.9809% <100.0000%> (ø)
...codehaus/groovy/classgen/asm/InvocationWriter.java	86.5702% <0.0000%> (ø)
...groovy/classgen/asm/sc/StaticInvocationWriter.java	74.8731% <66.6667%> (-0.1269%)	⬇️

... and 3 files with indirect coverage changes

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