feat: dynamically load injector configuration

[RomainMuller]

Use the config.Loader to dynamically load the injector configuration
everywhere, and not just in orchestrion pin.

[RomainMuller]

[codecov]

Codecov Report

Attention: Patch coverage is 71.11111% with 26 lines in your changes missing coverage. Please review.

Project coverage is 63.91%. Comparing base (a8237ee) to head (fc18c44).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/injector/builtin/generator/main.go	53.33%	7 Missing and 7 partials ⚠️
internal/jobserver/buildid/version.go	76.31%	4 Missing and 5 partials ⚠️
internal/toolexec/aspect/oncompile.go	71.42%	1 Missing and 1 partial ⚠️
internal/injector/config/validate.go	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #393      +/-   ##
==========================================
- Coverage   64.23%   63.91%   -0.33%     
==========================================
  Files         185      185              
  Lines       11087    10912     -175     
==========================================
- Hits         7122     6974     -148     
+ Misses       3420     3416       -4     
+ Partials      545      522      -23     

Components	Coverage Δ
Generators	76.69% <54.83%> (-1.43%)	⬇️
Instruments	73.41% <ø> (ø)
Go Driver	80.16% <ø> (ø)
Toolexec Driver	73.81% <71.42%> (-0.20%)	⬇️
Aspects	78.57% <100.00%> (+4.47%)	⬆️
Injector	77.13% <66.66%> (+2.16%)	⬆️
Job Server	67.99% <76.31%> (-5.47%)	⬇️
Integration Test Suite	57.14% <ø> (ø)
Other	63.91% <71.11%> (-0.33%)	⬇️

Files with missing lines	Coverage Δ
internal/injector/aspect/advice/assign.go	75.00% <ø> (+5.76%)	⬆️
internal/injector/aspect/advice/block.go	76.00% <ø> (+5.62%)	⬆️
internal/injector/aspect/advice/call.go	82.90% <ø> (+2.10%)	⬆️
internal/injector/aspect/advice/code/template.go	83.83% <ø> (+1.07%)	⬆️
internal/injector/aspect/advice/import.go	86.66% <ø> (+10.19%)	⬆️
internal/injector/aspect/advice/inject.go	80.00% <ø> (+6.31%)	⬆️
internal/injector/aspect/advice/struct.go	69.69% <ø> (+3.98%)	⬆️
internal/injector/aspect/advice/wrap.go	80.64% <ø> (+4.88%)	⬆️
internal/injector/aspect/aspect.go	71.66% <100.00%> (+15.52%)	⬆️
internal/injector/aspect/join/all-of.go	85.18% <ø> (+8.04%)	⬆️
... and 16 more

... and 3 files with indirect coverage changes

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