vim: Add motion support for toggle comments (#14919)

### Summary

This PR adds support for count and object motions to the toggle comments
action in Vim mode. The relevant issue is
[#14337](https://github.com/zed-industries/zed/issues/14337).

For example, `2 g c j` will toggle comments three lines downward. `g c g
g` will toggle comments from the current cursor position up to the start
of the file.

Notably missing from this PR are `g c b` (toggle comments for the
current block) as well as `g c p` (toggle comments for the current
paragraph). These seem to be non-standard.

The new module `normal/toggle_comments.rs` has been copied almost
verbatim from `normal/indent.rs`. Maybe that ought to be abstracted over
but I feel I lack the overview.

Release Notes:

- vim: Added support for count and object motion to the toggle comments
action ([#14337](https://github.com/zed-industries/zed/issues/14337)).

crates/vim/src/vim.rs

@@ -677,6 +677,7 @@ impl Vim {
                 | Operator::Lowercase
                 | Operator::Uppercase
                 | Operator::OppositeCase
+                | Operator::ToggleComments
         ) {
             self.start_recording(cx)
         };