[llvm] [RISCV][GlobalISel] Legalize scalable vectorized G_ADD, G_SUB, G_AND, G_OR, and G_XOR (PR #71400)

[Michael Maitland via llvm-commits]

michaelmaitland wrote:

Can you update PR description, as that will be used for commit body?

https://github.com/llvm/llvm-project/pull/71400