Consolidate GitHub Actions workflows

[danepowell]

There's a couple of potential improvements for the test and deploy workflows:

• Either combine them into a single workflow or use the uploaded artifact from the test workflow to perform the deploy workflow. Right now they duplicate a lot of the boilerplate setup code, this increases the maintenance burden, causes confusion as in Fix deploys #137, and means that the actual released code is different than the tested code.
• Stop using the deprecated actions actions/create-release and actions/upload-release-asset
• Right now the release is triggered by pushing a tag (sans release). Document this, and/or consider triggering releases from the GitHub release UI so it's a little more intuitive.

[typhonius]

One thing I've just noticed about release 0.0.12 is that there's no phar bundled for people to download and use. Is that a symptom if this issue, of #137 or just a manual release that didn't use the composer command? I think that's why I created the workflows as they were although it was a while ago so I'm not 100%.

[typhonius]

Oh actually it looks like it tried to do that here but the tag was created already: https://github.com/typhonius/acquia-logstream/runs/5890011417?check_suite_focus=true