vim: Add support for vim::PreviousLineStart motion (#14193)

Release Notes:

- vim: Added `-`/`+` to go to beginning of line above/below
([#14183](https://github.com/zed-industries/zed/issues/14183)).
- vim: (Breaking) Removed non-standard builtin binding from `-` to open
the project panel. You can re-add it to your keymap file with:
`{"context":"VimControl", "bindings":{ "-":
"pane::RevealInProjectPanel"}}`


Optionally, include screenshots / media showcasing your addition that
can be included in the release notes.


https://github.com/zed-industries/zed/assets/32429059/0e9e9348-265e-4a81-a45a-4739034dc5d9

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/vim/src/test.rs

@@ -1279,3 +1279,22 @@ async fn test_find_multibyte(cx: &mut gpui::TestAppContext) {
         .await
         .assert_eq(r#"<label for="guests">ˇo</label>"#);
 }
+
+#[gpui::test]
+async fn test_plus_minus(cx: &mut gpui::TestAppContext) {
+    let mut cx = NeovimBackedTestContext::new(cx).await;
+
+    cx.set_shared_state(indoc! {
+        "one
+           two
+        thrˇee
+    "})
+        .await;
+
+    cx.simulate_shared_keystrokes("-").await;
+    cx.shared_state().await.assert_matches();
+    cx.simulate_shared_keystrokes("-").await;
+    cx.shared_state().await.assert_matches();
+    cx.simulate_shared_keystrokes("+").await;
+    cx.shared_state().await.assert_matches();
+}