feat: add env-value-from as opt-in check for #705

[Nexusrex18]

Implements env-value-from check from #705 as opt-in (via config.yaml 'include'). If maintainers prefer, can add to default checks in a follow-up.

[codecov]

Codecov Report

❌ Patch coverage is 42.24138% with 67 lines in your changes missing coverage. Please review.
✅ Project coverage is 26.02%. Comparing base (dbd7529) to head (8a2e5bf).
⚠️ Report is 184 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/templates/envvarvaluefrom/template.go	50.51%	40 Missing and 8 partials ⚠️
...ates/envvarvaluefrom/internal/params/gen-params.go	0.00%	19 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1032       +/-   ##
===========================================
- Coverage   62.36%   26.02%   -36.35%     
===========================================
  Files         197      233       +36     
  Lines        4854     7302     +2448     
===========================================
- Hits         3027     1900     -1127     
- Misses       1439     5242     +3803     
+ Partials      388      160      -228     

Flag	Coverage Δ
unit	26.02% <42.24%> (-36.35%)	⬇️

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