vim test redux (#11709)

This cleans up the neovim-backed vim tests:
- removed exempted tests (we'll rely on bug reports to find missing edge
cases)
- moved all assertions into non-async fn's so that failures are
reporting on the right file/line
- removed the NeovimBackedBindingTestContext
- renamed a few things to make them clearer
- reduced the number of permutations tested in some cases to reduce
slowest test from 60s to 5s

Release Notes:

- N/A

crates/vim/test_data/test_visual_yank.json

@@ -20,6 +20,7 @@
 {"ReadRegister":{"name":"\"","value":"lazy d"}}
 {"Key":"shift-v"}
 {"Key":"y"}
+{"Get":{"state":"The quick brown\nfox jumps over\nˇthe lazy dog","mode":"Normal"}}
 {"ReadRegister":{"name":"\"","value":"the lazy dog\n"}}
 {"Put":{"state":"The ˇquick brown\nfox jumps over\nthe lazy dog"}}
 {"Key":"v"}