Prototype f64x2.nearest on ARM for both ARM v7 and ARM v8. ARM v8 has
support for vrintn, and for ARM v7 we fallback to runtime.

Since ARM v8 uses vrintn, which is the same instruction used for
F64RoundTiesEven (scalar), wasm-compiler reuses the Float64RoundTiesEven
check.

Bug: v8:10553
Change-Id: Ia4c4245cac87c132331f54e81dad323fc3fb9f6d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2268358Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68619}