python/driver/sqlite: add ability to load_extension

[judahrand]

The standard library sqlite3 module has the methods

conn.enable_load_extension(enabled: bool)`
conn.load_extenstion(extenstion: str)

if Python is compiled with --enable-loadable-sqlite-extensions.

It would be nice if such options were provided by the ADBC driver (perhaps enabled by default?). I'm thinking that extensions such as https://github.com/phiresky/sqlite-zstd would be incredibly valuable for use cases where talking to sqlite using ADBC makes sense.

[lidavidm]

It might be reasonable; at least we should make sure the sqlite we ship is compiled with extension loading enabled so that you can use the SQL function that loads extensions

[lidavidm]

CC @ywc88

I think we should:

• Add a new database option that corresponds to toggling sqlite3_enable_load_extension
• Add a new database option whose value is a path that will be passed to sqlite3_load_extension
• Add the option to the Python enum and add some unit tests
• Possibly, subclass Connection in adbc_driver_sqlite.dbapi and add these two extension methods