[VP][VE] Default VP_SREM/UREM to Expand and add generic expansion using VP_SDIV/UDIV+VP_MUL+VP_SUB.

I want to default all VP operations to Expand. These 2 were blocking
because VE doesn't support them and the tests were expecting them
to fail a specific way. Using Expand caused them to fail differently.

Seemed better to emulate them using operations that are supported.

@simoll mentioned on Discord that VE has some expansion downstream. Not
sure if its done like this or in the VE target.

Reviewed By: frasercrmck, efocht

Differential Revision: https://reviews.llvm.org/D133514