Make buffer search aware of search direction (#24974)

This solves a couple of issues with Vim search by making the search
buffer and `SearchableItem` aware of the direction of the search. If
`SearchOptions::BACKWARDS` is set, all operations will be reversed. By
making `SearchableItem` aware of the direction, the correct active match
can be selected when searching backward.

Fixes #22506. This PR does not fix the last problem in that issue, but
that one is also tracked in #8049.

Release Notes:

- Fixes incorrect behavior of backward search in Vim mode

crates/assistant_context_editor/src/context_editor.rs

@@ -54,7 +54,7 @@ use ui::{
     Tooltip,
 };
 use util::{maybe, ResultExt};
-use workspace::searchable::SearchableItemHandle;
+use workspace::searchable::{Direction, SearchableItemHandle};
 use workspace::{
     item::{self, FollowableItem, Item, ItemHandle},
     notifications::NotificationId,
@@ -3060,12 +3060,13 @@ impl SearchableItem for ContextEditor {
 
     fn active_match_index(
         &mut self,
+        direction: Direction,
         matches: &[Self::Match],
         window: &mut Window,
         cx: &mut Context<Self>,
     ) -> Option<usize> {
         self.editor.update(cx, |editor, cx| {
-            editor.active_match_index(matches, window, cx)
+            editor.active_match_index(direction, matches, window, cx)
         })
     }
 }