[mdatagen] generate goleak package test

[codeboten]

This automates the generation of package_test.go for any component that uses mdatagen.

The following configuration can be used to skip or ignore certain funcs:

tests:
  goleak:
    skip: true

tests:
  goleak:
    ignore:
      top:
        - "go.opencensus.io/stats/view.(*worker).start"

[crobert-1]

There's an open issue in the contrib repository for this with some discussion. Might be good to add a reference in the PR description, or copy/move it to core?

[crobert-1]

Thanks for doing this, automatically generating the tests will be really helpful 👍

[crobert-1]

I'm not very familiar with the inner-workings of mdatagen, but would it be very hard to modify so that sub-packages also have goleak generated?

For example:

.//consumer/consumertest/package_test.go
.//consumer/consumererror/package_test.go
.//consumer/package_test.go

One of the potential challenges of this is that each subdir/package would need its own goleak options, as it may need skipped, or have its own ignores that we don't want in other packages.

It's likely out of the scope of this PR, just raising as something that could be done here, or will need to be done later.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 91.69%. Comparing base (29240d9) to head (ac03a83).

❗ Current head ac03a83 differs from pull request most recent head f4eb76f. Consider uploading reports for the commit f4eb76f to get more accurate results

Files	Patch %	Lines
cmd/mdatagen/main.go	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9959      +/-   ##
==========================================
- Coverage   91.70%   91.69%   -0.02%     
==========================================
  Files         358      358              
  Lines       16543    16546       +3     
==========================================
+ Hits        15171    15172       +1     
- Misses       1045     1046       +1     
- Partials      327      328       +1     

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[songy23]

Need a rebase