Give resolve_const_param_in_non_trivial_anon_const more contextual information

[compiler-errors]

Hm, it would be really nice if we could actually pass a more rich description of the position that's disallowing the const, probably via the AnonConstKind, so that we don't have to say "here" but instead something like "in array repeat expressions" or "in const generic args" something.

Right now the errors just say "here", but I think we could pass in enough information in the resolver to know what position a non-trivial const arg actually is, which would greatly help discovery of the issue.

Originally posted by @compiler-errors in #142157 (review)