docs: generate documentation for integrations in dd-trace-go

[RomainMuller]

Restores the documentation generation facility, sourcing integrations
from the gopkg.in/DataDog/dd-trace-go.v1 package instead of the (now
removed) builtin package.

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 30 lines in your changes missing coverage. Please review.

Project coverage is 69.61%. Comparing base (2acdb1b) to head (b916163).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/injector/config/visitor.go	0.00%	14 Missing ⚠️
internal/injector/config/config-yml.go	40.00%	9 Missing ⚠️
internal/injector/config/config-go.go	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #510      +/-   ##
==========================================
- Coverage   72.15%   69.61%   -2.55%     
==========================================
  Files         104      104              
  Lines        5402     5427      +25     
==========================================
- Hits         3898     3778     -120     
- Misses       1044     1185     +141     
- Partials      460      464       +4     

Components	Coverage Δ
Generators	83.23% <ø> (ø)
Instruments	∅ <ø> (∅)
Go Driver	77.58% <ø> (-0.72%)	⬇️
Toolexec Driver	69.83% <ø> (-3.80%)	⬇️
Aspects	74.63% <ø> (-4.42%)	⬇️
Injector	74.10% <16.66%> (-4.17%)	⬇️
Job Server	70.26% <ø> (ø)
Other	69.61% <16.66%> (-2.55%)	⬇️

Files with missing lines	Coverage Δ
internal/injector/config/config.go	86.20% <ø> (ø)
internal/injector/config/config-go.go	66.66% <0.00%> (-7.18%)	⬇️
internal/injector/config/config-yml.go	56.62% <40.00%> (-4.25%)	⬇️
internal/injector/config/visitor.go	0.00% <0.00%> (ø)

... and 27 files with indirect coverage changes