Closes https://github.com/zed-industries/zed/issues/6916

Specification:
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspaceEdit
Adds a safe minimum of the capabilities that Zed supports already,
allowing rust-analyzer to send file edits on rename.

Release Notes:

- Fixed rust module rename from editor not renaming the FS entries
([6916](https://github.com/zed-industries/zed/issues/6916))