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/language/src/buffer.rs

@@ -37,6 +37,7 @@ use smallvec::SmallVec;
 use smol::future::yield_now;
 use std::{
     any::Any,
+    borrow::Cow,
     cell::Cell,
     cmp::{self, Ordering, Reverse},
     collections::BTreeMap,
@@ -2490,7 +2491,11 @@ impl BufferSnapshot {
     /// Returns [`IndentSize`] for a given position that respects user settings
     /// and language preferences.
     pub fn language_indent_size_at<T: ToOffset>(&self, position: T, cx: &AppContext) -> IndentSize {
-        let settings = language_settings(self.language_at(position), self.file(), cx);
+        let settings = language_settings(
+            self.language_at(position).map(|l| l.name()),
+            self.file(),
+            cx,
+        );
         if settings.hard_tabs {
             IndentSize::tab()
         } else {
@@ -2823,11 +2828,15 @@ impl BufferSnapshot {
 
     /// Returns the settings for the language at the given location.
     pub fn settings_at<'a, D: ToOffset>(
-        &self,
+        &'a self,
         position: D,
         cx: &'a AppContext,
-    ) -> &'a LanguageSettings {
-        language_settings(self.language_at(position), self.file.as_ref(), cx)
+    ) -> Cow<'a, LanguageSettings> {
+        language_settings(
+            self.language_at(position).map(|l| l.name()),
+            self.file.as_ref(),
+            cx,
+        )
     }
 
     pub fn char_classifier_at<T: ToOffset>(&self, point: T) -> CharClassifier {
@@ -3529,7 +3538,8 @@ impl BufferSnapshot {
         ignore_disabled_for_language: bool,
         cx: &AppContext,
     ) -> Vec<IndentGuide> {
-        let language_settings = language_settings(self.language(), self.file.as_ref(), cx);
+        let language_settings =
+            language_settings(self.language().map(|l| l.name()), self.file.as_ref(), cx);
         let settings = language_settings.indent_guides;
         if !ignore_disabled_for_language && !settings.enabled {
             return Vec::new();