Add set_authorizer support for fine-grained access control

[alec]

https://docs.python.org/3/library/sqlite3.html#sqlite3.Connection.set_authorizer

Example:

import sqlite3

async def restrict_drops(action_code, arg1, arg2, db_name, trigger_name):
    # Deny all DROP operations
    if action_code == sqlite3.SQLITE_DROP_TABLE:
        return sqlite3.SQLITE_DENY
    # Allow everything else
    return sqlite3.SQLITE_OK

await conn.set_authorizer(restrict_drops)

Perf Test	Iterations	Duration	Rate
inserts	11939	2.0s	5968.8/s
inserts_authorized	11841	2.0s	5919.7/s