This patch extends the preliminary support for vector-predicated (VP)
operation legalization to include promotion of illegal integer vector
types.
Integer promotion of binary VP operations is relatively simple and
piggy-backs on the non-VP logic, but passing the two extra mask and VP
operands through to the promoted operation.
Tests have been added to the RISC-V target to cover the basic scenarios
for integer promotion for both fixed- and scalable-vector types.
clang-format: please reformat the code