indent guides: Respect language specific settings in multibuffers (#12528)

Indent guides can be configured per language, meaning that in a multi
buffer we can get excerpts where indent guides should be
disabled/enabled/styled differently than other excerpts.

Imagine the following scenario, i have indent guides disabled in my
settings, but want to enable them for JS and Python. I also want to use
a different line width for python files. Something like this is now
supported:

<img width="445" alt="image"
src="https://github.com/zed-industries/zed/assets/53836821/0c91411c-145c-4210-a883-4c469d5cb828">

And the relevant settings for the example above:
```json
"indent_guides": {
  "enabled": false
},
"languages": {
  "JavaScript": {
    "indent_guides": {
      "enabled": true
    }
  },
  "Python": {
    "indent_guides": {
      "enabled": true,
      "line_width": 5
    }
  }
}
```



Release Notes:

- Respect language specific settings when showing indent guides in a
multibuffer
- Fixes an issue where indent guide specific settings were not
recognized when specified in local settings

crates/language/src/buffer.rs

@@ -6,7 +6,7 @@ pub use crate::{
 };
 use crate::{
     diagnostic_set::{DiagnosticEntry, DiagnosticGroup},
-    language_settings::{language_settings, LanguageSettings},
+    language_settings::{language_settings, IndentGuideSettings, LanguageSettings},
     markdown::parse_markdown,
     outline::OutlineItem,
     syntax_map::{
@@ -542,25 +542,10 @@ pub struct IndentGuide {
     pub end_row: BufferRow,
     pub depth: u32,
     pub tab_size: u32,
+    pub settings: IndentGuideSettings,
 }
 
 impl IndentGuide {
-    pub fn new(
-        buffer_id: BufferId,
-        start_row: BufferRow,
-        end_row: BufferRow,
-        depth: u32,
-        tab_size: u32,
-    ) -> Self {
-        Self {
-            buffer_id,
-            start_row,
-            end_row,
-            depth,
-            tab_size,
-        }
-    }
-
     pub fn indent_level(&self) -> u32 {
         self.depth * self.tab_size
     }
@@ -3151,9 +3136,15 @@ impl BufferSnapshot {
     pub fn indent_guides_in_range(
         &self,
         range: Range<Anchor>,
+        ignore_disabled_for_language: bool,
         cx: &AppContext,
     ) -> Vec<IndentGuide> {
-        let tab_size = language_settings(self.language(), None, cx).tab_size.get() as u32;
+        let language_settings = language_settings(self.language(), self.file.as_ref(), cx);
+        let settings = language_settings.indent_guides;
+        if !ignore_disabled_for_language && !settings.enabled {
+            return Vec::new();
+        }
+        let tab_size = language_settings.tab_size.get() as u32;
 
         let start_row = range.start.to_point(self).row;
         let end_row = range.end.to_point(self).row;
@@ -3234,6 +3225,7 @@ impl BufferSnapshot {
                         end_row: last_row,
                         depth: next_depth,
                         tab_size,
+                        settings,
                     });
                 }
             }