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 83.65385% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.16%. Comparing base (dbd7529) to head (4c224e9).
⚠️ Report is 189 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/templates/envvarvaluefrom/template.go	85.39%	9 Missing and 4 partials ⚠️
...ates/envvarvaluefrom/internal/params/gen-params.go	73.33%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1032       +/-   ##
===========================================
- Coverage   62.36%   28.16%   -34.20%     
===========================================
  Files         197      235       +38     
  Lines        4854     6295     +1441     
===========================================
- Hits         3027     1773     -1254     
- Misses       1439     4362     +2923     
+ Partials      388      160      -228     

Flag	Coverage Δ
unit	28.16% <83.65%> (-34.20%)	⬇️

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