make the materalize cr namespaced

[doy-materialize]

Motivation

this allows us to move the backend configuration to a kubernetes secret, which this pr also does, and also remove all setup and cleanup of the data created by the database in favor of just having the credentials provided to us

Checklist

• [x] This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• [x] This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• [x] If this PR evolves an existing $T ⇔ Proto$T mapping (possibly in a backwards-incompatible way), then it is tagged with a T-proto label.
• [x] If this PR will require changes to cloud orchestration or tests, there is a companion cloud PR to account for those changes that is tagged with the release-blocker label (example).
• [x] If this PR includes major user-facing behavior changes, I have pinged the relevant PM to schedule a changelog post.