[Github Actions] Separate Flutter Analyze from pub.dev validation

[vbuberen]

Description

This PR separates Flutter analyze step from validations if pub.dev requirements are met for publishing. This change will provide more clarity when something fails from publishing point of view or the code analyzer.

For further updates for even better granularity I would move more operations to corresponding plugins workflows and run all_plugins workflows only after merging the PR, while run all validations/checks in the corresponding plugin related workflow.

Related Issues

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the Flutter Style Guide.
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

[miquelbeltran]

Looks good to me!