Use package:pubspec_parse

[xvrh]

This is a proposal to replace package:pubspec by package:pubspec_parse. pubspec_parse is a package owned by the Dart team and seems to have a better quality score. Also it exposes more fields (like repository, issueTracker...)

[leoafarias]

@xvrh that makes sense, I believe initially the other package was chosen due to less dependencies and we were having a lot of conflicts with yaml, collection and so on, but maybe these issues have been worked out.

[xvrh]

@leoafarias in terms of dependencies, this is also a win:

These packages are no longer being depended on:
- pubspec 2.2.0
- quiver 3.1.0
- uri 1.0.0

pubspec_parse was already pulled as a the transitive dependency.

[leoafarias]

@xvrh can you fix the metrics test on this PR to make sure there is no issues with your previous PR?

[xvrh]

@leoafarias done, I rebased my PR on top of the latest main