repl: standardize Control key indications

Throughout our messages and docs, we refer to the Control key in a
surprisingly varied number of ways:

* Control
* Ctrl
* Cntl
* varied capitalization on the above (e.g., ctrl vs. Ctrl)

Then, in key combinations:

* One of the items from the previous list followed by `-`
* ... or followed by `+`
* ... surrounded or not by `<` and `>`
* ... and inside backticks or not
* ... or just `^`

This is the start of standardization on the formulation recommended by
the Microsoft Style Guide (e.g., **Ctrl+C**).

PR-URL: https://github.com/nodejs/node/pull/35270


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>