Rollup merge of #102876 - SparrowLii:import-candidate, r=fee1-dead

suggest candidates for unresolved import

Currently we prompt suggestion of candidates(help notes of `use xxx::yyy`) for names which cannot be resolved, but we don't do that for import statements themselves that couldn't be resolved. It seems reasonable to add candidate help information for these statements as well.
Fixes #102711

Author: matthiaskrgr