filter.utils.muxer: validate parameters using param-validation

This patch makes filter.utils.muxer validate its parameters using the
param-validation utility.  The muxer component doesn't accept any
parameters, but at least this makes it verify that it doesn't receive
any unexpected parameter.

Change-Id: Ia89313c9b9b1fddd244b757a235be201ff5eb230
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/2156