Split nightly-rosetta-*-build-test.yaml into build and test files

[DwarKapex]

No description provided.

[terrykong]

Initially the workflows were separate, but they were merged in order to allow the publishing of the :latest tag to be contingent on the test results.

We can revisit when there's BW, but I think when splitting, the container publishing logic should be:

1. Run rosetta build workflow
   1. publish :nightly-YYYY-MM-DD tag if build successful
2. Run rosetta test workflow on :nightly-YYYY-MM-DD (if workflow_run), :latest (if workflow_dispatch)
   1. publish :latest if tests successful

As an aside, by re-splitting the workflows, we'll be at the limit for workflow run chaining (3 levels max). Not a blocker since I don't think we'll go beyond that in the near future.