require clamping of index for OpVectorExtractDyanmic, OpVectorInsertDynamic, and bitfield insert and extract

[dneto0]

This eliminates a source of undefined behaviour.

[Kangz]

Maybe I misunderstand the title, shouldn't this be handled by implementations as a code transform instead? I'm not sure how easy it is to spec that the application has to do it.

[dneto0]

Yes, the implementation has to ensure that these instructions behave as if clamped. The shader coming into the implementation doesn't have to do anything special to get this behaviour.