Auto merge of #147196 - LorrensP-2158466:same-res-ambiguity-test, r=petrochenkov

Test: Ambigious bindings in same namespace with the same res

Add a test based on the discussion [here](https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/near/542316157) and related to rust-lang/rust#145575 (comment).

This is the most reduced form I could create that passes on nightly but fails with rust-lang/rust#145108 (see [#gsoc > Project: Parallel Macro Expansion @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/near/542335131)).

Also not sure about the test names.

r? `@petrochenkov`

Author: bors