test/utils: add operator aliases for lowlevel-blt-bench

test/utils: add operator aliases for lowlevel-blt-bench

Lowlevel-blt-bench uses the operator alias "outrev". Add an alias for it
in the operator-name table.

Also add aliases for overrev, inrev and atoprev, so that
lowlevel-blt-bench can later recognize them for new test cases.

The aliases are added such, that an operator to name lookup will never
return them; it returns the proper names instead.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Ben Avison <bavison@riscosopen.org>