Adds DatabaseBootstrapTrait and OsposConfigFixtureTrait to replace
duplicated per-file setUp()/tearDown() bootstrap and OSPOS config mock
boilerplate across test classes, bringing them in line with the
ItemsControllerTest gold-standard shape.
Fixes the real root cause of tabular_helperTest's suite-order-dependent
failure: dropAllForeignKeyConstraints()/foreignKeyExists()/
dropColumnIfExists() temporarily blank the shared connection's DBPrefix
via overridePrefix() but never restored it if the query between the two
calls threw (e.g. migration_helperTest's mocked-failure tests) -
permanently corrupting prefixed table lookups for the rest of the
process. Wrapped each in try/finally. Also widens executeScript() to
accept an explicit connection so migration SQL can't silently run
against the wrong DB group.
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
