Test infallible alignment errors in Fuchsia, then remove `Ref` `unaligned` constructors

[joshlf]

With #1718, we can likely remove the unaligned constructors from Ref. However, we should first confirm that this is doable by vendoring #1718 into Fuchsia and attempting to remove all unaligned uses from tree.

[joshlf]

Vendored into Fuchsia successfully.