Add publish workflow

[agocs]

What does this PR do?

Adds a github action that publishes the latest datadog-lambda-java to a Sonatype staging repository when a new version is tagged.

Motivation

Testing Guidelines

Additional Notes

Types of changes

• [ ] Bug fix
• [ ] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Checklist

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog