Implement i64x2 widen i32x4, and saturating rounding multiply high.

Port: 9cb7e571

Port: 39f2e3de
Change-Id: Ib88aca3e3f66eb4a12be4d2cf4e51ac930849cc0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2632353Reviewed-by: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Commit-Queue: Zhao Jiazhong <zhaojiazhong-hf@loongson.cn>
Auto-Submit: Liu yu <liuyu@loongson.cn>
Cr-Commit-Position: refs/heads/master@{#72109}