ICE Fix #16562

Fixes #16562

Detect ty_err in fixup_substs and return None instead of failing.
In search_for_vtable return vtable_error in both early and non-early
if fixup_substs returns None. This was asserting previously. I don't
know anything about the early vs. non-early stages and whether this
is significant or not.

Reduced the amount of data being printed to the debug log in
tydecode.rs. It was printing several megabytes of metadata.
Each new file needs a proper license header.