feat: add spec parser and combiner for grubby_info

[JoySnow]

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Complete Description of Additions/Changes:

RHINENG-15118

• add new spec and parser for grubby_info_all
• add combiner for grubby commands

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.03%. Comparing base (9c64871) to head (c1f020f).
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4329      +/-   ##
==========================================
+ Coverage   76.98%   77.03%   +0.04%     
==========================================
  Files         735      736       +1     
  Lines       41306    41366      +60     
  Branches     8772     8789      +17     
==========================================
+ Hits        31801    31865      +64     
+ Misses       8439     8438       -1     
+ Partials     1066     1063       -3     

Flag	Coverage Δ
unittests	77.01% <100.00%> (+0.04%)	⬆️

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[xiangce]

We may use this new Grubby combiner to deprecate the existing BootLoaderEntries

[xiangce]

As a combiner, it would be good to combine more useful attribute here, e.g. devs can use the combiner rather than access each single parser to fetch particular info.