vim: Handle paste in visual line mode when cursor is at newline (#30791)

This Pull Request fixes the current paste behavior in vim mode, when in
visual mode, and the cursor is at a newline character. Currently this
joins the pasted contents with the line right below it, but in vim this
does not happen, so these changes make it so that Zed's vim mode behaves
the same as vim for this specific case.

Closes #29270 

Release Notes:

- Fixed pasting in vim's visual line mode when cursor is on a newline
character

crates/vim/test_data/test_paste_visual.json

@@ -41,3 +41,11 @@
 {"Key":"p"}
 {"Get":{"state":"ˇfox jumps over\nthe lazy dog","mode":"Normal"}}
 {"ReadRegister":{"name":"\"","value":"The quick brown\n"}}
+{"Put":{"state":"ˇThe quick brown\nfox jumps over\nthe lazy dog"}}
+{"Key":"y"}
+{"Key":"y"}
+{"Key":"shift-v"}
+{"Key":"j"}
+{"Key":"$"}
+{"Key":"p"}
+{"Get":{"state":"ˇThe quick brown\nthe lazy dog","mode":"Normal"}}