Summary

Closes #2312

This PR enables Biome to read and understand nested .gitignore files, and eventually ignore them in CLI and LSP.

In order to achieve that, I applied the following refactors:

• created a new ExtensionHandler that understands ignore files.
• updated DocumentFileSource, and added a new function called can_read. This function is used in the following places
  • Inside open_file_internal. We bail if Biome can't read a certain file
  • Inside can_handle of the traverse.rs file. Now Biome won't throw an error if it can read a file
• Changed the type of Document::syntax, inside the workspace server. This type holds the content a file, and its parsed tree. Now, the parsed tree is a Option, because a file can be read from disk, but can't be parsed. This the case for ignore files.
• The VCS configuration is now mapped into a new type called VcsSettings. These settings are used to query if a file is ignored.
• The WorkspaceServer now has a new method called update_project_ignore_files, which is in charge of updating the project Settings::vcs_settings with the ignore files that were discovered after the project was scanned. This method does what the former method did: read the file from disk, and create a Gitignore type. As per the new feature, we now have a root Gitignore, the ignore file found in the project's root. Then we have a list of Gitgnore, which represents the nested ignore files; these are different because they must be matched against the folder they are contained to, so they are treated differently.

Test Plan

We have very similar tests that were repeated across CLI commands, I removed them and placed them inside the cases/ folder, using the TemporaryFs, which should help with the testing.

I also tested it manually using our own repository. I did remove dist/ from the ignore file, and added a new .gitignore inside the tailwind package. The CLI correctly ignores the file inside the dist/ folder (created upon compilation). I also checked that VSCode, upon file opening, doesn't provide diagnostics and doesn't format the files. Fortunately the logs are helpful and I could see that the file was ignored.