SQLite3::close() called from within a userland function, aggregate,
collation or authorizer callback freed the registered statements and
functions while sqlite3 was still executing, corrupting the active
statement and crashing the request. Track callback re-entry with a
per-database counter shared by all four callback kinds and throw an
Error from close() while it is non-zero; the database stays usable and
can be closed after the query completes.
Closes GH-23650
