chore(actions): run test suite against PRs and on label

[ashwinkumar6]

Description of changes

Currently, to run e2e tests before merging a PR we need to manually push the changes to another branch on upstream and update the push-integ-test workflow by updating the trigger branch name. With this change you can directly add the run-tests label and it should start running the E2E tests.

Implementation reference taken from UI

(Note: currently only configured for main/release. Can be updated to all branches if required)

Conditions

1. PR shouldn't be raised from fork
2. PR should contain the run-tests label
3. PR should raised to main/release (added, can remove)

Description of how you validated changes

Tested the following flows

Flow 1

1. Raise a PR from upstream to main/release without the 'run-tests' tag. [Not Trigger]
2. Add 'run-tests' tag [Triggered]
3. Push new commit [New Trigger]

Flow 2

1. Raise a PR from upstream to main/release with the 'run-tests' tag. [Triggered]
2. Push new commit [New Trigger]
3. Remove 'run-tests' tag, push new commit [Not Triggered]

Failure case (CI run)

Success case (CI run)

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[AllanZhengYP]

Thanks for the example runs and explanation. Maybe we should remove this action: https://github.com/aws-amplify/amplify-js/blob/main/.github/workflows/push-integ-test.yml since it's essentially replaced by this change.