Introduce StructuredRunOpt for more complex runopts

[AbishekS]

Summary: StructuredRunOpt can be used to create new complex runopts

This can be used as for example:

    dataclass
    class UlimitTest(StructuredRunOpt):
        name: str
        hard: int
        soft: int

        def template(self) -> str:
            return "{name},{soft},{hard}"

This comes with

1. template() that helps the from_repr() use that template to map to the fields with types
2. eq to check equality between two

Differential Revision: D85159071

[meta-codesync[bot]]

@AbishekS has exported this pull request. If you are a Meta employee, you can view the originating Diff in D85159071.

[codecov-commenter]

Codecov Report

:x: Patch coverage is 88.88889% with 3 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 91.61%. Comparing base (dd683f4) to head (9a6da96).

Files with missing lines	Patch %	Lines
torchx/specs/api.py	88.88%	3 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1154      +/-   ##
==========================================
- Coverage   91.63%   91.61%   -0.02%     
==========================================
  Files          84       84              
  Lines        6595     6619      +24     
==========================================
+ Hits         6043     6064      +21     
- Misses        552      555       +3     

Flag	Coverage Δ
unittests	91.61% <88.88%> (-0.02%)	:arrow_down:

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