[batch-release] Step2 : Publish packages from the release branch

[hannah-hyj]

issue: https://github.com/flutter/flutter/issues/176944

Add a batch Release Flag in the publish command.

The main branch will only publish packages that are opted out of batch release. The release branch will only publish packages that are opted into batch release.

Pre-Review Checklist

• [ ] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [ ] I read the Tree Hygiene page, which explains my responsibilities.
• [ ] I read and followed the relevant style guides and ran the auto-formatter.
• [ ] I signed the CLA.
• [ ] The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• [ ] I linked to at least one issue that this PR fixes in the description above.
• [ ] I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under[^1].
• [ ] I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under[^1].
• [ ] I updated/added any relevant documentation (doc comments with ///).
• [ ] I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under[^1].
• [ ] All existing and new tests are passing.

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[flutter-dashboard[bot]]

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.