Add key contexts for Pickers (#35665)

Closes: https://github.com/zed-industries/zed/issues/35430

Added:
- Workspace > CommandPalette
- Workspace > GitBranchSelector
- Workspace > GitRepositorySelector
- Workspace > RecentProjects
- Workspace > LanguageSelector
- Workspace > IconThemeSelector
- Workspace > ThemeSelector

Release Notes:

- Added new keymap contexts for various Pickers - CommandPalette,
GitBranchSelector, GitRepositorySelector, RecentProjects,
LanguageSelector, IconThemeSelector, ThemeSelector

crates/command_palette/src/command_palette.rs

@@ -136,7 +136,10 @@ impl Focusable for CommandPalette {
 
 impl Render for CommandPalette {
     fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
-        v_flex().w(rems(34.)).child(self.picker.clone())
+        v_flex()
+            .key_context("CommandPalette")
+            .w(rems(34.))
+            .child(self.picker.clone())
     }
 }