[mdatagen] copy files from contrib to core

[codeboten]

This is to allow us to use it in core as well

[codecov]

Codecov Report

Attention: 240 lines in your changes are missing coverage. Please review.

Comparison is base (1c84578) 91.39% compared to head (bccb66b) 90.54%.

Files	Patch %	Lines
cmd/mdatagen/main.go	43.06%	95 Missing and 24 partials ⚠️
cmd/mdatagen/loader.go	54.54%	60 Missing and 5 partials ⚠️
...md/mdatagen/internal/metadata/generated_metrics.go	90.61%	23 Missing ⚠️
cmd/mdatagen/metricdata.go	80.30%	12 Missing and 1 partial ⚠️
cmd/mdatagen/internal/metadata/generated_config.go	82.08%	8 Missing and 4 partials ⚠️
...d/mdatagen/internal/metadata/generated_resource.go	91.11%	4 Missing ⚠️
cmd/mdatagen/internal/metadata/generated_status.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9172      +/-   ##
==========================================
- Coverage   91.39%   90.54%   -0.86%     
==========================================
  Files         320      330      +10     
  Lines       17208    18195     +987     
==========================================
+ Hits        15728    16475     +747     
- Misses       1177     1383     +206     
- Partials      303      337      +34     

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[hughesjj]

Super happy/excited with this change, and LGTM

[mx-psi]

Should this be at https://github.com/open-telemetry/opentelemetry-go-build-tools instead?

[songy23]

Should this be at https://github.com/open-telemetry/opentelemetry-go-build-tools instead?

Seems no because of dependency issue. (mdatagen depends on core while core depends on build-tools)

[mx-psi]

Let's leave it here then :) AFAICT the dependency is just on the autogenerated code used for testing, which we could split off into a separate module to avoid a circular module dependency, but no need to do this now