Primary key improvements (UUID and existing PK column support)

[zackkrida]

This project enhances Mathesar's import and table creation workflows by allowing users to set primary keys (PKs) as either auto-incrementing integers (identity) or random UUIDv4 values (uuid).

During import, Mathesar will default to adding a new PK column, giving users the option to select either an identity or uuid type. Alternatively, if an existing column meets Mathesar's uuid or identity requirements, users can designate it as the primary key instead.

Additionally, users will be able to set the value of any primary key column when inserting rows in the table view.