mdatagen: get package name from metadata

[braydonk]

Description

I noticed a mistake in my previous PR #11232; some function calls did not pass the correct package name in (passing in "metadata" instead of the intended generated package name). This PR attempts to address the potential for this mistake to even occur by providing a wrapper generateFile function that automatically uses the generated package name from the metadata. The original version of the function that accepts a package name is intact for the templates that are going in the base package instead of the generated one.

Link to tracking issue

Bug originally from #11231
Fixes #11469

Testing

make mdatagen-test

Also added a custom generated package to the sample components, which would have caught the original bug.

Documentation

[braydonk]

I believe this change should not need a changelog. It is a fix for a bug that never made it into a release, and otherwise provides no user-visible changes.

[codecov]

Codecov Report

Attention: Patch coverage is 87.23748% with 79 lines in your changes missing coverage. Please review.

Project coverage is 91.36%. Comparing base (ef79a0e) to head (32052b5).

Files with missing lines	Patch %	Lines
...amplereceiver/internal/custom/generated_metrics.go	91.83%	27 Missing and 2 partials ⚠️
...plereceiver/internal/custom/generated_telemetry.go	63.79%	21 Missing ⚠️
...samplereceiver/internal/custom/generated_config.go	82.85%	8 Missing and 4 partials ⚠️
...ampleprocessor/internal/custom/generated_config.go	83.78%	4 Missing and 2 partials ⚠️
...pleprocessor/internal/custom/generated_resource.go	91.11%	4 Missing ⚠️
...mplereceiver/internal/custom/generated_resource.go	91.11%	4 Missing ⚠️
cmd/mdatagen/internal/command.go	66.66%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11468      +/-   ##
==========================================
- Coverage   91.46%   91.36%   -0.10%     
==========================================
  Files         435      441       +6     
  Lines       23757    24369     +612     
==========================================
+ Hits        21729    22265     +536     
- Misses       1650     1718      +68     
- Partials      378      386       +8     

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[braydonk]

The new coverage issue are just for the generated custom package I added, which I don't think are any more/less covered than the other generated metadata package and are just there as goldens anyway. So I think the codecov can be accepted.