[objects] Migrate kHoleNanInt64 unboxed doubles to uninitialized values during boilerplate serialization

Boilerplate values may possess an unboxed double field filled with the kHoleNan64Int sentinel value, which indicates that the field is uninitialized. When a boilerplate value migrates away from the unboxed double representation to a tagged one, we should replace the sentinel value by the proper uninitialized oddball value.

This fixes an issue with JSCreateLowering::AllocateFastLiteral not detecting const stores of uninitialized values properly.

R=bmeurer@chromium.org, jarin@chromium.org

Bug: chromium:976598
Change-Id: I6bb216c0618a3105e6c8cfc04b1900d2f83a52ce
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1674034Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Georg Schmid <gsps@google.com>
Cr-Commit-Position: refs/heads/master@{#62394}