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/editor/src/display_map.rs

@@ -423,11 +423,12 @@ impl DisplayMap {
     }
 
     fn tab_size(buffer: &Model<MultiBuffer>, cx: &mut ModelContext<Self>) -> NonZeroU32 {
+        let buffer = buffer.read(cx).as_singleton().map(|buffer| buffer.read(cx));
         let language = buffer
-            .read(cx)
-            .as_singleton()
-            .and_then(|buffer| buffer.read(cx).language());
-        language_settings(language, None, cx).tab_size
+            .and_then(|buffer| buffer.language())
+            .map(|l| l.name());
+        let file = buffer.and_then(|buffer| buffer.file());
+        language_settings(language, file, cx).tab_size
     }
 
     #[cfg(test)]