Add more allowed return values for relaxed trunc unsigned

[ngzhian]

These values show up due to faster algorithms used for relaxed trunc unsigned when hardware does not support single-instruction lowering.

See https://github.com/WebAssembly/relaxed-simd/pull/140 for more discussions.

[ngzhian]

@yurydelendik @Maratyszcza

[yurydelendik]

Nice. The 0x80000000 and 0xfffffffe are now included.

Thanks.

[ngzhian]

either/or is a construct introduced by the threads proposal https://github.com/WebAssembly/threads/blob/main/interpreter/text/lexer.mll#L455 would you prefer to have a comment in the tests referencing the threads proposal?

[dtig]

Thanks yeah, please add it so its easier to find.