APK for Couchbase PHP on Alpine Linux

We currently depend on the community supported package for testing the Couchbase PHP extension on Alpine Linux. However we need to start publishing an APK package ourselves both for internal testing purposes and so we can release an "officially" tested release.

The related issues will cover the ancillary work break down (and more may be created if needed) but the basic idea is the following:

• Create an APK that can be tested locally and follows standard to be submitted to the Alpine Linux package repository.
• Update CI/CD pipelines to be able to install from our own APK that is generated while testing release candidates and does not use the community APK package.
• Update documentation for instructions about how to install from this APK package (it's also possible to install from a custom repo that we host if there are any problems with the official repository or if needed immediately for a hot fix, etc).