Remove `abort_if_errors` before borrow checking

[estebank]

Filed as per #59903 (comment)

When removing abort_if_errors call right before borrow checking, the fallout from the change causes multiple duplicated errors (which can be deduplicated with little effort) and a couple of ICEs.

We should make an effort to fix these issues and remove the abort_if_errors call.

[estebank]

Once implemented, this will close #30999.

[estebank]

CC #30418, as eliding some of the errors caused by the removal fall under it.