Support .editorconfig (#19455)

Closes https://github.com/zed-industries/zed/issues/8534
Supersedes https://github.com/zed-industries/zed/pull/16349

Potential concerns:
* we do not follow up to the `/` when looking for `.editorconfig`, only
up to the worktree root.
Seems fine for most of the cases, and the rest should be solved
generically later, as the same issue exists for settings.json
* `fn language` in `AllLanguageSettings` is very hot, called very
frequently during rendering. We accumulate and parse all `.editorconfig`
file contents beforehand, but have to go over globs and match these
against the path given + merge the properties still.
This does not seem to be very bad, but needs more testing and
potentially some extra caching.


Release Notes:

- Added .editorconfig support

---------

Co-authored-by: Ulysse Buonomo <buonomo.ulysse@gmail.com>

crates/paths/src/paths.rs

@@ -293,3 +293,6 @@ pub fn local_tasks_file_relative_path() -> &'static Path {
 pub fn local_vscode_tasks_file_relative_path() -> &'static Path {
     Path::new(".vscode/tasks.json")
 }
+
+/// A default editorconfig file name to use when resolving project settings.
+pub const EDITORCONFIG_NAME: &str = ".editorconfig";