Get rid of dependency to cratedb-toolkit

[amotl]

Problem

CrateDB Toolkit includes a few SQLAlchemy patches reused by others. However, it must be removed as a dependency before upstreaming the adapter on behalf of GH-1, because it weighs in too heavy.

Solution

The incubating SQLAlchemy dialect for CrateDB will host the relevant SQLAlchemy patches and polyfills instead.

Action

There are already relevant patches at 80/20 status, which need to be completed, mostly by accompanying them with corresponding software tests and documentation sections.

The most prominent ones are likely those:

• Types: Add support for CrateDB's FLOAT_VECTOR data type and KNN_MATCH function crate/sqlalchemy-cratedb#9
• Database: Add autoincrement, uniqueness, and sync-writes polyfills crate/sqlalchemy-cratedb#28

[amotl]

Status Update

• Dependencies: Update to sqlalchemy-cratedb==0.38.0 crate/cratedb-examples#498
• Use SQLAlchemy patches and polyfills from sqlalchemy-cratedb crate/mlflow-cratedb#156