This removes the osbuild-composer-cloud package, binary, systemd units,
the (unused) test binary, and the (only-run-on-RHEL) test in aws.sh.
Instead, move the cloud API into the main package, using the same
socket as the koji API, osbuild-composer-api.socket. Expose it next to
the koji API on route `/api/composer/v1`.
This is a backwards incompatible change, but only of the -cloud parts,
which have been marked as subject to change.
