Use mdatagen to generate goleak tests in subpackages

[crobert-1]

Is your feature request related to a problem? Please describe.

mdatagen currently generates goleak checks for packages when enabled. However, it only adds goleak checks for the top level directory of the package.

Describe the solution you'd like

goleak checks generated for every sub directory that runs tests.

Additional context

https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/30483 https://github.com/open-telemetry/opentelemetry-collector-contrib/issues/30483#issuecomment-1889713415