buffer: allow Uint8Array input to methods

Allow all methods on `buffer` and `Buffer` to take `Uint8Array`
arguments where it makes sense. On the native side, there is
effectively no difference, and as a bonus the `isUint8Array`
check is faster than `instanceof Buffer`.

PR-URL: https://github.com/nodejs/node/pull/10236


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Сковорода Никита Андреевич <chalkerx@gmail.com>