Add --coverage-package option

[liamappelbe]

At the moment dart test only ever gathers coverage data for the current package. But sometimes part of out test coverage comes from other packages, especially in the case of monorepos.

To handle this case, flutter test has a --coverage-package option, which is a multi-option of RegExps. When this option is present, we list all the transitive packages the current package depends on, and include them in the coverage report if they match any of the RegExps.

This PR adds the exact same flag to dart test.

Fixes dart-lang/sdk#60958

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[DanTup]

@liamappelbe thank you! 🙂

Do you have an idea of when the next pkg:test release might be? (not a request to do one now, but I'd prefer to implement this once it's available so I can ensure I gate it correctly on the version that includes it).

[liamappelbe]

@liamappelbe thank you! 🙂

Do you have an idea of when the next pkg:test release might be? (not a request to do one now, but I'd prefer to implement this once it's available so I can ensure I gate it correctly on the version that includes it).

That's up to @natebosch. From my end, I'm fine publishing this asap.

[natebosch]

I have a few more changes I'd like to get out that have been slow to land internally. I expect I should have a release ready sometime next week.

[DanTup]

sgtm, thanks!