Rollup merge of #150155 - Aditya-PS-05:fix/ice-150103-root-in-suggestions, r=estebank

fix ICE when {{root}} appears in import suggestions

Fixes rust-lang/rust#150103

When wrong nested imports like `use A::{::Fish}` were used, the internal {{root}} would appear in diagnostic suggestions, causing an ICE in `join_path_idents` which asserted that **{{root}} should only appear at the start of a path**.

r? ``@matthiaskrgr``

Author: JonathanBrouwer