n-api: improve performance creating strings

Improve performance creating strings using N-API by ensuring that the
strings are not internalized.

Added test cases for latin-1 and utf-16 strings.

PR-URL: https://github.com/nodejs/node/pull/26439
Fixes: https://github.com/nodejs/node/issues/26437


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>