[riscv][wasm] Introduce F16 value type

Port commit 06847fbb


Change-Id: I3fb708c7e3a55a02443484f743ffa1c4f3c3c31c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/5716343


Reviewed-by: Ji Qiu <qiuji@iscas.ac.cn>
Commit-Queue: Yahan Lu <yahan@iscas.ac.cn>
Cr-Commit-Position: refs/heads/main@{#95119}