terraform test: Add some interesting td files and make the cleanup more robust, speed up mz-debug build

[def-]

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.

[bobbyiliev]

Seems like some tests are failing with:

error: executing query failed: db error: ERROR: unknown cluster replica size 1
--
  | HINT: Valid cluster replica sizes are: mz_probe, 25cc, 50cc, 100cc, 200cc, 300cc, 400cc, 600cc, 800cc, 1200cc, 1600cc, 3200cc, 6400cc: ERROR: unknown cluster replica size 1
  | HINT: Valid cluster replica sizes are: mz_probe, 25cc, 50cc, 100cc, 200cc, 300cc, 400cc, 600cc, 800cc, 1200cc, 1600cc, 3200cc, 6400cc
  | \|
  | 10 \| > DROP CLUSTER IF EXISTS gh_6942_cluster CASCADE;
  | 11 \| > CREATE CLUSTER gh_6942_cluster SIZE '1', REPLICATION FACTOR 1;
  | \| ^

[def-]

Finally a green run: https://buildkite.com/materialize/nightly/builds/11904
Edit: After my latest fixes: https://buildkite.com/materialize/nightly/builds/11905

[bobbyiliev]

Looks good!