vim: Support ranges in command (#15985)

The most requested feature here is "search and replace in visual mode",
but as a happy side effect we can now support things like :2,12j to join
those lines, and much much more.



Release Notes:

- vim: Added support for range syntax in command
([#9428](https://github.com/zed-industries/zed/issues/9428)).
- vim: Prefill command with `:'<,'>` from visual mode
([#13535](https://github.com/zed-industries/zed/issues/13535)).

crates/editor/src/selections_collection.rs

@@ -393,7 +393,7 @@ impl<'a> MutableSelectionsCollection<'a> {
         self.collection.display_map(self.cx)
     }
 
-    fn buffer(&self) -> Ref<MultiBufferSnapshot> {
+    pub fn buffer(&self) -> Ref<MultiBufferSnapshot> {
         self.collection.buffer(self.cx)
     }