Remove unused plugin crates (#8350)

This PR removes the unused crates for plugin support.

We're currently exploring Wasm-based extensions, and it's unlikely that
we'll be reusing any of this existing work.

Release Notes:

- N/A
401798d9b8Marshall Bowers committed on 2/25/2024, 12:05:18 AM· committed by GitHubparent35bec98
24 files changedLine totals unavailable