feat: injector config loader API

[RomainMuller]

Adds a new internal/injector/config package that provides features to load injector configuration, and also to inspect whether packages contain such configuration (so it can be used to implement orchestrion pin's -prune and -validate features.

[codecov]

Codecov Report

Attention: Patch coverage is 56.04027% with 131 lines in your changes missing coverage. Please review.

Project coverage is 60.47%. Comparing base (e6d1010) to head (a4a7af4).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/injector/config/config-yml.go	45.36%	42 Missing and 11 partials ⚠️
internal/injector/config/config-go.go	56.47%	31 Missing and 6 partials ⚠️
internal/pin/pin.go	59.57%	17 Missing and 2 partials ⚠️
internal/injector/config/config.go	69.44%	9 Missing and 2 partials ⚠️
internal/injector/config/validate.go	61.11%	4 Missing and 3 partials ⚠️
internal/injector/builtin/generator/main.go	63.63%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #391      +/-   ##
==========================================
- Coverage   60.86%   60.47%   -0.40%     
==========================================
  Files         175      179       +4     
  Lines       12343    12593     +250     
==========================================
+ Hits         7513     7615     +102     
- Misses       4349     4481     +132     
- Partials      481      497      +16     

Components	Coverage Δ
Generators	76.72% <63.63%> (-0.19%)	⬇️
Instruments	88.05% <ø> (ø)
Go Driver	73.94% <ø> (ø)
Toolexec Driver	70.66% <ø> (ø)
Aspects	71.88% <100.00%> (+0.03%)	⬆️
Injector	72.21% <55.02%> (-1.53%)	⬇️
Job Server	64.58% <ø> (+0.56%)	⬆️
Integration Test Suite	54.24% <ø> (ø)
Other	60.47% <56.04%> (-0.40%)	⬇️

Files with missing lines	Coverage Δ
internal/cmd/pin.go	100.00% <100.00%> (ø)
internal/injector/aspect/aspect.go	52.45% <100.00%> (+1.61%)	⬆️
internal/pin/auto.go	69.35% <100.00%> (ø)
internal/injector/builtin/generator/main.go	73.78% <63.63%> (-0.73%)	⬇️
internal/injector/config/validate.go	61.11% <61.11%> (ø)
internal/injector/config/config.go	69.44% <69.44%> (ø)
internal/pin/pin.go	47.71% <59.57%> (-10.16%)	⬇️
internal/injector/config/config-go.go	56.47% <56.47%> (ø)
internal/injector/config/config-yml.go	45.36% <45.36%> (ø)

... and 3 files with indirect coverage changes