rorfs for cacheless lacks write access to /tmp/ to generate cache

[grokspawn]

Description of the change:
when we are using extractContent, but w/o extractContent.CacheDir, ensure that we have write permissions to /tmp/ by creating an emptydir volume there.

Motivation for the change:
When there is no provided CacheDir, our recent changes to set SecurityContext{ReadOnlyFilesystem: ptr.To(true)} will not allow writing to /tmp/. However, opm will need to generate a cache and cannot be told another directory to use.

Architectural changes:

Testing remarks:
#3614 passed CI with no errors, both unit which covered ExtractContent functionality including w/o CacheDir.

This is because while the unit tests validated the shape of the resulting pods but not the pods' viability in a cluster (i.e. could the pods walk the initcontainer chain successfully and bring the GRPC service up).

ginkgo test "gRPC address catalog source" does evaluate catsrc pod viability using extractContent, but never as cacheless.

Reviewer Checklist

• Implementation matches the proposed design, or proposal is updated to match implementation
• Sufficient unit test coverage
• Sufficient end-to-end test coverage
• Bug fixes are accompanied by regression test(s)
• e2e tests and flake fixes are accompanied evidence of flake testing, e.g. executing the test 100(0) times
• tech debt/todo is accompanied by issue link(s) in comments in the surrounding code
• Tests are comprehensible, e.g. Ginkgo DSL is being used appropriately
• Docs updated or added to /doc
• Commit messages sensible and descriptive
• Tests marked as [FLAKE] are truly flaky and have an issue
• Code is properly formatted

[openshift-ci]

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