[DirectX] audit the list of trivially scalarizable dxil ops

[spall]

Audit the list of trivially scalarizable dxil ops and add any missing ones to 'DirectXTTIImpl::isTargetIntrinsicTriviallyScalarizable'

[bob80905]

Make sure all intrinsics in DirectXIntrinsics.td are either in that function referenced above, have issues made so that they're added, or have a documented reason as for why they are not going to be included in the switch table.