[TableGen] Add support constraining a vector type in a pattern to have a specific...

[TableGen] Add support constraining a vector type in a pattern to have a specific element type and for constraining a vector type to have the same number of elements as another vector type. This is useful for AVX512 mask operations so we relate the mask type to the type of the other arguments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231356 91177308-0d34-0410-b5e6-96231b3b80d8