Avoid instruction selector to emit sign extension instruction after most
`xxx.w` instructions in RV64I and RV64M, because `xxx.w` instructions
will automatically sign-extend the result

Change-Id: Ia4291242dc3e51f49be1e6dda2d5a3365b5e7bfa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3536845Reviewed-by: Yahan Lu <yahan@iscas.ac.cn>
Commit-Queue: Yahan Lu <yahan@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#79537}