GA Migrations PreCommit Java Sharding Examples

[fernando-wizeline]

As part of the migration of Precommit and Postcommit Jobs from Jenkins to GA in self-hosted runners, this PR contains:

Migrated workflow job-precommit-beam-examples.yml

The migrated workflow was added to CI.md

DO NOT MERGE until the effort to use self-hosted runners is completed https://github.com/apache/beam/pull/22703

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• [ ] Choose reviewer(s) and mention them in a comment (R: @username).
• [ ] Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• [ ] Update CHANGES.md with noteworthy changes.
• [ ] If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI.