findNvim - Add an option to "stop searching after a match"

[xiyaowong]

I think this title needs no further explanation. :)

[justinmk]

It probably should do this by default, rather than making it optional.

The main (intended) reason that findNvim returns multiple results is for the case where none of the results are valid, and then the caller can mention these results in a user-facing error message, like:

Nvim X.Y not found. Found:

- /usr/local/bin/nvim 0.3 (too old)
- /foo/bar/nvim (failed to run)
- ...

Edit: OTOH, maybe it's useful to be able to select the most-recent Nvim, when there are multiple valid matches.