restructure container registry layout

for nightly containers use:
containers.ligo.org/lscsoft/lalsuite/lalsuite:nightly-${PLATFORM}

and for tags use:
containers.ligo.org/lscsoft/lalsuite/lalsuite:${VERSION}-${PLATFORM}

this will allow container cleanup to work in a more sensible way
42 jobs for container-cleanup in 141 minutes and 33 seconds (queued for 9 seconds)
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