This PR updates all GitHub workflows to use the latest major versions of key Go-related actions:
* **actions/checkout:** upgraded from `v4` → **`v5`**
* **actions/setup-go:** upgraded from `v5` → **`v6`**
Using Docker ENTRYPOINT should allow for configuration of running
versitygw within Docker container similar to how the systemd
service is setup with environment variables.
This also adds the backends azure and plugin to the acceptable
backend options for both docker and systemd.
Fixes#1335
There was a breaking change in latest awscli. This will tie the tests
to the known working version until we can get a more permanenet fix
for aws cli in place.
