Create GH actions workflow for agent release

[JonasKunz]

What does this PR do?

Add GH actions workflow for our existing release process.
Most of the process is unchanged, main difference is that all commiting / tagging is done in the very first job within the workflow and not during the actual build and deploy anymore.

I added a new automation for moving eveything in the unreleased section in the changelog to a new section for the target release.

As a result, we should now be able to retry the individual steps in this workflow, because each one is atomic and retriable in case of failure.

I testes the provided jobs as far as possible without authorization on my own fork.
The following things still need to be done:

• Implement the actual buildkite integration for the mvn deploy
• Implement the AWS Lambda build
• Setup the apmmachine authorization (or whichever user we use)

I have marked all the places with # TODO comments in the workflow file where work is needed.

[ghost]

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• Start Time: 2023-04-06T14:39:20.817+0000

• Duration: 13 min 0 sec

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🤖 GitHub comments

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To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• run benchmark tests : Run the benchmark tests.

• run jdk compatibility tests : Run the JDK Compatibility tests.

• run integration tests : Run the Agent Integration tests.

• run end-to-end tests : Run the APM-ITs.

• run windows tests : Build & tests on windows.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[JonasKunz]

Closed in favor of #3137