buffer: add type check in bidirectionalIndexOf

Add a type check in bidirectionalIndexOf to avoid using something else
as Buffer. This may happen if e.g. lastIndexOf is called with invalid
this.

PR-URL: https://github.com/nodejs/node/pull/32770
Fixes: https://github.com/nodejs/node/issues/32753
Fixes: https://github.com/nodejs/node/issues/32747


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>