sql-150: Create test suite for durable temporary objects

[SangJunBak]

Creates a more in-depth test suite for implementation, included unit tests at the persist level and e2e tests at the mzcompose level to replicate killing a process

Motivation

sql-150

Description

catalog: test ephemeral item reclamation in the durable layer

Temporary items are durable items tagged with the UUID of the session that created them. Neither of the two mechanisms holding that together had any coverage.

• read-write: name uniqueness is scoped by the owning session, so two sessions can each hold a tt in the sentinel temporary schema while one session cannot hold it twice. remove_ephemeral_items then reclaims all of them and leaves normal items alone, which matters because an over-broad filter there would silently delete real user items.
• open: a writable open reclaims a temporary item left behind by a process that died without closing its session, which is the only thing between a kill -9 and a permanently leaked catalog item. A read-only open must not, since a zero-downtime follower reads the leader's catalog while the leader's sessions are still live and still own theirs. The read-only case is checked before the writable one, so the ordering makes both directions observable.

test: cover temporary item cleanup on session close and kill -9

Temporary tables and views are durable catalog items tagged with their owning session, so they need cleanup on both paths out of a session, and neither path had a test. The only existing temp-teardown coverage is DISCARD TEMP / DISCARD ALL, which is a different code path.

test: cover 0dt preflight behavior for temporary items

Ensure creating temporary items during a 0dt upgrade doesn't cause a halt. This is already the case because even though these temporary objects are public to all envds, we clear them from the snapshot whenever we open the catalog not in readonly mode.

[linear-code]

SQL-150

[def-]

Thanks for extra tests!

[mtabebe]

Thank you for the tests 🫡