Simplify the item info collection visitor running before late resolution

[oli-obk]

r? @petrochenkov

I mainly want 52cc1ac (use item collection in late resolution visitor), as my first step to refactor use item lowering needs to track the owner, which the info collection visitor doesn't do right now, and it seems annoying to add when there is a perfectly good visitor already tracking it right there.

I tried getting rid of the info collection visitor entirely, but counting the number of generic lifetime parameters of free items is necessary for diagnostics in the late visitor when visiting paths. A path can refer to an item that is visited later, so we haven't recorded the number of generic lifetime parameters yet (if we do it in the late visitor). If we collect them in the def collector, we have to handle macro invocations in generic parameter definition position. It wasn't clear to me how to handle that without severe spaghetti code, so the visitor stays around for now.

[petrochenkov]

counting the number of generic lifetime parameters of free items is necessary for diagnostics in the late visitor when visiting paths

Same is true for delegation_fn_sigs and item_required_generic_args_suggestions, both are used in compiler\rustc_resolve\src\late\diagnostics.rs in "out of order" way (and not just for delegations, before delegations that table was called fn_has_self or something like that). Upd: delegation_fn_sigs is no longer used for delegation lowering anymore, it again acts only as fn_has_self.

Not sure about resolve_eii.

At least use_items doesn't seem to be affected.

[oli-obk]

I'll put the use_items commit directly into the PR that needs it