Types: Add support for CrateDB's `FLOAT_VECTOR` data type and `KNN_MATCH` function

[amotl]

About

CrateDB's FLOAT_VECTOR data type, and its accompanying KNN_MATCH function, have been added with CrateDB 5.5.0. This patch adds corresponding SQLAlchemy type and function/predicate support.

Details

Those two implementetations have been predecessors, and both sites will be used to verify this patch, after it has been merged.

• LangChain Vector Store: vectorstores/cratedb/sqlalchemy_type.py
• Meltano CrateDB Target: sqlalchemy/vector.py

Backlog

• [x] Documentation
• [x] Software tests

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.74%. Comparing base (6b64619) to head (9557d1c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #9 +/- ## ========================================== + Coverage 84.65% 85.74% +1.08% ========================================== Files 14 15 +1 Lines 919 989 +70 ========================================== + Hits 778 848 +70 Misses 141 141 ``` | [Flag](https://app.codecov.io/gh/crate-workbench/sqlalchemy-cratedb/pull/9/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=crate-workbench) | Coverage Δ | | |---|---|---| | [main](https://app.codecov.io/gh/crate-workbench/sqlalchemy-cratedb/pull/9/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=crate-workbench) | `85.74% <100.00%> (+1.08%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=crate-workbench#carryforward-flags-in-the-pull-request-comment) to find out more.

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