feat: Vector Search

[MarkDuckworth]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

Fixes #<issue_number_goes_here> 🦕

[wu-hui]

I reviewed by commits, maybe my comments no longer apply if you already fixed them in a different commits.

The comments are minor anyways, so LGTM!

[sofisl]

Please remove the breaking changes:

query.toProto() --> query._toProto()

for this release