feat(ISV-6785): parse labels in containerfiles

[jedinym]

Added parsing of labels from containerfiles so our parser can fully replace dockerfile-json in konflux-build-cli.

I also decided to encapsulate the parsed stages into a Containerfile struct for easier future expandability.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.68421% with 20 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.39%. Comparing base (ca12216) to head (0eeff39).

Files with missing lines	Patch %	Lines
pkg/containerfile/containerfile.go	71.11%	10 Missing and 3 partials ⚠️
cmd/capo/main.go	0.00%	5 Missing ⚠️
cmd/buildprobe/main.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   60.30%   61.39%   +1.09%     
==========================================
  Files           9        9              
  Lines         985     1018      +33     
==========================================
+ Hits          594      625      +31     
+ Misses        306      305       -1     
- Partials       85       88       +3     

Flag	Coverage Δ
integration-tests	56.96% <26.86%> (-5.35%)	⬇️
unit-tests	38.60% <69.73%> (+1.85%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
pkg/buildargs/buildargs.go	90.24% <100.00%> (+3.57%)	⬆️
pkg/probe/probe.go	79.66% <100.00%> (ø)
pkg/scan.go	77.99% <100.00%> (ø)
cmd/buildprobe/main.go	0.00% <0.00%> (ø)
cmd/capo/main.go	0.00% <0.00%> (ø)
pkg/containerfile/containerfile.go	80.83% <71.11%> (-0.73%)	⬇️

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