Pgvector

- Added `schema` option for asyncpg

- Improved support for cursor factories with Psycopg 2

- Fixed `invalid memory alloc request size` error

If upgrading from 0.2.7 or 0.3.0, [recreate](https://github.com/pgvector/pgvector/blob/v0.3.1/README.md#031) all `ivfflat` indexes after upgrading to ensure all data is indexed.

- Fixed issue with inserts silently corrupting `ivfflat` indexes (introduced in 0.2.7)
- Fixed segmentation fault with index creation when lists > 6500

- Added support for Postgres 15
- Dropped support for Postgres 9.6

- Fixed `unexpected data beyond EOF` error