keymap: Update Prev to Previous for consistency (#25909)

Closes #10167

This is take 2 on https://github.com/zed-industries/zed/pull/2341 which
was closed due to lack of migrator.

This PR contains rename of following keymap actions: 
```sh
1. ["editor::GoToPrevHunk", { "center_cursor": true }] -> ["editor::GoToPreviousHunk", { "center_cursor": true }]
2. "editor::GoToPrevDiagnostic" -> "editor::GoToPreviousDiagnostic"
3. "editor::ContextMenuPrev" -> "editor::ContextMenuPrevious"
4. "search::SelectPrevMatch" -> "search::SelectPreviousMatch"
5. "file_finder::SelectPrev" -> "file_finder::SelectPrevious"
6. "menu::SelectPrev" -> "menu::SelectPrevious"
7. "editor::TabPrev" -> "editor::Backtab"
```

Release Notes:

- Renamed several keymap actions for consistency (e.g., `GoToPrevHunk` →
`GoToPreviousHunk`, `TabPrev` → `Backtab`). Your existing configured
keybindings will still work. You can click **"Backup and Update"** at
the top of your keymap file to easily update to the new actions.


Co-authored-by: Joseph T. Lyons <JosephTLyons@gmail.com>

crates/tab_switcher/src/tab_switcher_tests.rs

@@ -1,7 +1,7 @@
 use super::*;
 use editor::Editor;
 use gpui::{TestAppContext, VisualTestContext};
-use menu::SelectPrev;
+use menu::SelectPrevious;
 use project::{Project, ProjectPath};
 use serde_json::json;
 use std::path::Path;
@@ -64,7 +64,7 @@ async fn test_open_with_prev_tab_selected_and_cycle_on_toggle_action(
         assert_match_selection(tab_switcher, 3, tab_1.boxed_clone());
     });
 
-    cx.dispatch_action(SelectPrev);
+    cx.dispatch_action(SelectPrevious);
     tab_switcher.update(cx, |tab_switcher, _| {
         assert_eq!(tab_switcher.delegate.matches.len(), 4);
         assert_match_at_position(tab_switcher, 0, tab_4.boxed_clone());