This PR adds a new function, `make-file-executable`, to the Zed
extension API that can be used to mark a given file as executable
(typically the language server binary).

This is available in v0.0.5 of the `zed_extension_api` crate.

We also reworked how we represent the various WIT versions on disk to
make it a bit clearer what the version number entails.

Release Notes:

- N/A

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Co-authored-by: Max <max@zed.dev>