buffer: check byteLength in readInt(B|L)E

The 'byteLength' argument should be required and of type 'number'.
It should have a value between 1 and 6.

PR-URL: https://github.com/nodejs/node/pull/11146
Fixes: https://github.com/nodejs/node/issues/10515


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>