Ignore non-file workspace URL (#12725)
## Summary
This PR updates the server to ignore non-file workspace URL.
This is to avoid crashing the server if the URL scheme is not "file".
We'd still raise an error if the URL to file path conversion fails.
Also, as per the docs of
[`to_file_path`](https://docs.rs/url/2.5.2/url/struct.Url.html#method.to_file_path):
> Note: This does not actually check the URL’s scheme, and may give
nonsensical results for other schemes. It is the user’s responsibility
to check the URL’s scheme before calling this.
resolves: #12660
## Test Plan
I'm not sure how to test this locally but the change is small enough to
validate on its own.
