Some more CheckPrereq/CheckArguments cleanup

For a few LUs, a few tests in, or even the whole CheckPrereq, can be
moved to CheckArguments, as they don't touch state and only do a 'type'
validation.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>