fix: support helm chart import-values

[emmanuel-ferdman]

PR Summary

When linting helm charts that use import-values to pull values from subcharts, kube-linter was failing with a nil pointer error because those imported values were never actually loaded. This PR adds a call to ProcessDependencies before rendering templates, which is what helm itself does in its template.go.

Fixes #1111

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 29.44%. Comparing base (dbd7529) to head (6b3587f).
⚠️ Report is 255 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1112       +/-   ##
===========================================
- Coverage   62.36%   29.44%   -32.92%     
===========================================
  Files         197      237       +40     
  Lines        4854     6452     +1598     
===========================================
- Hits         3027     1900     -1127     
- Misses       1439     4385     +2946     
+ Partials      388      167      -221     

Flag	Coverage Δ
unit	29.44% <100.00%> (-32.92%)	⬇️

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[janisz]

@emmanuel-ferdman nice, could you add a unit test of e2e test to verify it?