In #5510 we changed the value types of these variants from u{32,64} to
f{32,64}. One side effect of this change was that two NaN values would
no longer compare equal. While this is behavior complies with IEEE-754
floating point operations, it broke equality assumptions in fuzzing.
This commit changes equality for Val to make NaNs compare equal. Since
the component model requires NaN canonicalization, all NaN bit
representations compare equal, which is different from the original
behavior.
This also gives Vals the semantics of Eq again, so that trait impl has
been reintroduced to related types as well.
9156cca8ca