tty: truecolor check moved before 256 check

256 color would be return instead of 16m if both env variables were set

* tty: improve color check order highest spec first
* tty: add test for TERM and COLORTERM set
* tty: move COLORTERM check outside TERM closure
* tty: remove extra if check for COLORTERM

Refs: https://github.com/nodejs/node/issues/27609

PR-URL: https://github.com/nodejs/node/pull/30474


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>