[HLSL] Add appropriate validation for MD_range metadata kind

[bob80905]

The MD_range metadata kind needs better validation, so that it mimics the validation in DXC.
Currently, all MD_range metadata node kinds are accepted. However, there needs to be further checks, like in DXC.
For example, in DXC, Verifier.cpp has a function, visitRangeMetadata that validates the range metadata node kind. One check, among many, is that the number of operands must be even. This needs to be validated to allow this metadata type in the whitelist.

[inbelic]

This issue is concerned with insuring that MD_range is validation in the same manner as the DXIL validator in DXC.

From here the only verification DXC did was the checks in LLVM/IR/Verifier.cpp. I have verified that the checks done in upstream llvm Verifier.cpp are equivalent.

Since MD_range has already been added to the whitelist, this issue can be closed as completed.