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/editor/src/editor.rs

@@ -7192,7 +7192,7 @@ impl Editor {
         });
     }
 
-    pub fn tab_prev(&mut self, _: &TabPrev, window: &mut Window, cx: &mut Context<Self>) {
+    pub fn backtab(&mut self, _: &Backtab, window: &mut Window, cx: &mut Context<Self>) {
         if self.move_to_prev_snippet_tabstop(window, cx) {
             return;
         }
@@ -9236,7 +9236,7 @@ impl Editor {
 
     pub fn context_menu_prev(
         &mut self,
-        _: &ContextMenuPrev,
+        _: &ContextMenuPrevious,
         _window: &mut Window,
         cx: &mut Context<Self>,
     ) {
@@ -11263,7 +11263,7 @@ impl Editor {
 
     fn go_to_prev_diagnostic(
         &mut self,
-        _: &GoToPrevDiagnostic,
+        _: &GoToPreviousDiagnostic,
         window: &mut Window,
         cx: &mut Context<Self>,
     ) {
@@ -11476,7 +11476,7 @@ impl Editor {
 
     fn go_to_prev_hunk(
         &mut self,
-        action: &GoToPrevHunk,
+        action: &GoToPreviousHunk,
         window: &mut Window,
         cx: &mut Context<Self>,
     ) {