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_paste_visual_block.json

@@ -3,6 +3,7 @@
 {"Key":"2"}
 {"Key":"j"}
 {"Key":"y"}
+{"Get":{"state":"The ˇquick brown\nfox jumps over\nthe lazy dog","mode":"Normal"}}
 {"ReadRegister":{"name":"\"","value":"q\nj\nl"}}
 {"Key":"p"}
 {"Get":{"state":"The qˇquick brown\nfox jjumps over\nthe llazy dog","mode":"Normal"}}
@@ -19,6 +20,7 @@
 {"Key":"ctrl-v"}
 {"Key":"j"}
 {"Key":"y"}
+{"Get":{"state":"The ˇquick brown\nfox jumps over\nthe lazy dog","mode":"Normal"}}
 {"ReadRegister":{"name":"\"","value":"q\nj"}}
 {"Key":"l"}
 {"Key":"ctrl-v"}