Route admin CREATE/DROP DATABASE through a short-lived postgres.js maintenance
connection instead of spawning psql via execSync per call, and remove the
redundant DROP-before-CREATE (db names are pid+random, never pre-exist).
Cuts ~2 of 3 subprocess forks per test across ~55 tests; the slowest core
test file drops from ~90s under full-suite contention (32.6s->27s standalone)
with all 75 tests still green.
Fusion-Task-Id: FN-SLOW-TEST
1efff4e83c