Allow icon themes to provide their own file associations (#24926)

This PR adds the ability for icon themes to provide their own file
associations.

The old `file_types.json` that was previously used to make these
associations has been removed in favor of storing them on the default
theme.

Icon themes have two new fields on them:

- `file_stems`: A mapping of file stems to icon keys.
- `file_suffixes`: A mapping of file suffixes to icon keys.

These mappings produce icon keys which can then be used in `file_icons`
to associate them to a particular icon:

```json
{
  "file_stems": {
    "Makefile": "make"
  },
  "file_suffixes": {
    "idr": "idris"
  },
  "file_icons": {
    "idris": { "path": "./icons/idris.svg" },
    "make": { "path": "./icons/make.svg" }
  }
}
```

When loading an icon theme, the `file_stems` and `file_icons` fields
will be merged with the ones from the base icon theme, with the values
from the icon theme being loaded overriding ones in the base theme.

Release Notes:

- Added the ability for icon themes to provide their own file
associations.

crates/outline_panel/src/outline_panel.rs

@@ -28,12 +28,12 @@ use file_icons::FileIcons;
 use fuzzy::{match_strings, StringMatch, StringMatchCandidate};
 use gpui::{
     actions, anchored, deferred, div, point, px, size, uniform_list, Action, AnyElement, App,
-    AppContext as _, AssetSource, AsyncWindowContext, Bounds, ClipboardItem, Context, DismissEvent,
-    Div, ElementId, Entity, EventEmitter, FocusHandle, Focusable, HighlightStyle,
-    InteractiveElement, IntoElement, KeyContext, ListHorizontalSizingBehavior, ListSizingBehavior,
-    MouseButton, MouseDownEvent, ParentElement, Pixels, Point, Render, ScrollStrategy,
-    SharedString, Stateful, StatefulInteractiveElement as _, Styled, Subscription, Task,
-    UniformListScrollHandle, WeakEntity, Window,
+    AppContext as _, AsyncWindowContext, Bounds, ClipboardItem, Context, DismissEvent, Div,
+    ElementId, Entity, EventEmitter, FocusHandle, Focusable, HighlightStyle, InteractiveElement,
+    IntoElement, KeyContext, ListHorizontalSizingBehavior, ListSizingBehavior, MouseButton,
+    MouseDownEvent, ParentElement, Pixels, Point, Render, ScrollStrategy, SharedString, Stateful,
+    StatefulInteractiveElement as _, Styled, Subscription, Task, UniformListScrollHandle,
+    WeakEntity, Window,
 };
 use itertools::Itertools;
 use language::{BufferId, BufferSnapshot, OffsetRangeExt, OutlineItem};
@@ -664,9 +664,8 @@ pub fn init_settings(cx: &mut App) {
     OutlinePanelSettings::register(cx);
 }
 
-pub fn init(assets: impl AssetSource, cx: &mut App) {
+pub fn init(cx: &mut App) {
     init_settings(cx);
-    file_icons::init(assets, cx);
 
     cx.observe_new(|workspace: &mut Workspace, _, _| {
         workspace.register_action(|workspace, _: &ToggleFocus, window, cx| {
@@ -6641,7 +6640,7 @@ outline: struct OutlineEntryExcerpt
             workspace::init_settings(cx);
             Project::init_settings(cx);
             project_search::init(cx);
-            super::init((), cx);
+            super::init(cx);
         });
     }