[LegalizeTypes][VP] Add promotion support for binary VP ops

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.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D108288