also check credit consumption limit on environmentd startup

[doy-materialize]

Motivation

https://github.com/MaterializeInc/database-issues/issues/9708

Tips for reviewer

not sure if there are other limits we want to check on startup, but this one is an important one to start with

we probably also want tests for this, but i'm about to head out for vacation for a week, so figured i would at least get this up before i left

Checklist

• This PR has adequate test coverage / QA involvement has been duly considered. (trigger-ci for additional test/nightly runs)
• This PR has an associated up-to-date design doc, is a design doc (template), or is sufficiently small to not require a design.
• 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.
• 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).
• If this PR includes major user-facing behavior changes, I have pinged the relevant PM to schedule a changelog post.