[mdatagen]: Use cobra for the command, add version flag

[bogdandrutu]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 69.56522% with 77 lines in your changes missing coverage. Please review.

Project coverage is 91.78%. Comparing base (d5215c5) to head (b1f38a2).
Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/mdatagen/internal/command.go	70.40%	53 Missing and 21 partials ⚠️
cmd/mdatagen/main.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11196      +/-   ##
==========================================
- Coverage   91.83%   91.78%   -0.06%     
==========================================
  Files         415      416       +1     
  Lines       19856    19869      +13     
==========================================
+ Hits        18235    18237       +2     
- Misses       1248     1260      +12     
+ Partials      373      372       -1     

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[atoulme]

LGTM. Your move of the code from main.go to internal/command.go shows we don't have enough test coverage for some of the templating functions, something we can spin into a new issue.

Filed #11219 to follow up.