Normalizes an AliasReft. This uses the trait solver to find the [ImplSourceUserDefinedData]
and uses the args there, which we map back to Flux via refining. This loses refinements,
but that’s fine because AliasReft should not rely on refinements for trait solving.
Normalize an rty::AliasTy by converting it to rustc, normalizing it using rustc api, and
then mapping the result back to rty. This will lose refinements and it should only be used
to normalize sorts because they should only contain unrefined types. However, we are also using
it as a hack to normalize types in cases where we fail to collect a candidate, this is unsound
and should be removed.