Add vim::MoveTo{Next,Prev} flags for regex and case sensitive search (#18429)

This makes the hard-coded regex and case-sensitive search flags in
`vim::MoveToNext` and `vim::MoveToPrev` commands configurable in key
bindings.

Example:

```json
{
  "context": "VimControl && !menu",
  "bindings": {
    "*": ["vim::MoveToNext", { "regex": false, "caseSensitive": false }],
    "#": ["vim::MoveToPrev", { "regex": false, "caseSensitive": false }]
  }
}
```

Closes #15837.

Release Notes:

- Added `regex` and `caseSensitive` arguments to `vim::MoveToNext` and
`vim ::MoveToPrev` commands, for toggling regex and case sensitive
search.