[3.11] gh-108550: Speed up sqlite3 tests (#108551) (#108567)

Disable the busy handler for all concurrency tests; we have full
control over the order of the SQLite C API calls, so we can safely
do this.

test_sqlite3.test_transactions now completes ~10 times faster than before.

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>