[thunderbiscuit]

This PR adds a workflow that would publish bdk-android to Maven Central using a workflow dispatch. It's a very similar workflow to what we used on bdk-jvm to release 3.1.1.

Fixes #1116.

A few things to note:

1. I didn't know you could do this, but a worfklow can basically just "call" another workflow and ensure it succeds before proceeding. This is what we do here, by running test-android.yaml before continuing with the release.
2. The library doesn't completely publish by the end of the workflow. It sits in a "ready to deploy" state on Maven Central, and an approved maintainer has to go and click "Publish" in the UI for the library to publish. This is similar to how we do it for the JVM library and React Native library on npm. We could eventually remove this requirement through a different command in the workflow, but I keep it like that for now as added protection against releasing an artifact we didn't intend to.

Checklists

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