Have HInvoke instructions know their number of actual arguments.

Add an art::HInvoke::GetNumberOfArguments routine so that
art::HInvoke and its subclasses can return the number of
actual arguments of the called method.  Use it in code
generators and intrinsics handlers.

Consequently, no longer remove a clinit check as last input
of a static invoke if it is still present during baseline
code generation, but ensure that static invokes have no such
check as last input in optimized compilations.

Change-Id: Iaf9e07d1057a3b15b83d9638538c02b70211e476