buffer: refactor Buffer.prototype.inspect()

Replace toString().match().join() with toString().replace().trim(). This
enables the elimination of a length check becuase replace() will return
empty string if Buffer is empty whereas match() returns null.

PR-URL: https://github.com/nodejs/node/pull/11600


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>