Misc improvement of the CI build

[Kailai-Wang]

Context

While working on #2140, I've noticed a few places that can be improved and I believe it's worth a separate issue/PR to make it more transparent.

Tasks:

• remove the :dev tag for litentry-worker and litentry-cli, latest is fine
• prefer pre-built image / minimal image over a standard base image then install everything manually
• do we need docker layer caches?
• do we need local registry? It's introduced in Apply caching for enclave CI build  #2156 to act as the base image for the subsequent stages
• shall we move some tests to other jobs to run them as concurrently as possible?
• better grouping of debugging output using ::group::

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