GROOVY-11655: Create extension method to make StringBuilder like a stack

[dongwq]

see:
https://issues.apache.org/jira/browse/GROOVY-11655

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes missing coverage. Please review.

Project coverage is 68.9955%. Comparing base (5916bc5) to head (d66fd8d).

Files with missing lines	Patch %	Lines
...g/codehaus/groovy/runtime/StringGroovyMethods.java	66.6667%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##               master      #2215        +/-   ##
==================================================
+ Coverage     68.9931%   68.9955%   +0.0024%     
- Complexity      29660      29665         +5     
==================================================
  Files            1423       1423                
  Lines          114323     114335        +12     
  Branches        19832      19833         +1     
==================================================
+ Hits            78875      78886        +11     
- Misses          28815      28816         +1     
  Partials         6633       6633                

Files with missing lines	Coverage Δ
...g/codehaus/groovy/runtime/StringGroovyMethods.java	83.0769% <66.6667%> (-0.1262%)	⬇️

... and 2 files with indirect coverage changes

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[paulk-asert]

Nice idea, but personally, I am unsure whether it is compelling enough to be added to Groovy. I will provide some comments anyway.

[eric-milles]

I don't think there is much general value in providing "stack of chars" semantic. You can always provide these for your own projects through extension or category class.

[dongwq]

I don't think there is much general value in providing "stack of chars" semantic. You can always provide these for your own projects through extension or category class.

@eric-milles ,
the issue try to solve the basic Use Case of String:

• in algorithms where you need to modify strings dynamically, such as backtracking or parsing tasks.

given some examples code here: https://issues.apache.org/jira/browse/GROOVY-11655