Resolve: stop letting items shadow reexported glob imports

[jseyfried]

This PR stops non-import items from shadowing glob-imported re-exports (fixes #31337) and fixes the fallout in the standard libraries and tests.

Previously, it was possible to shadow a glob-imported re-export, so this a [breaking-chage]. For example,

mod foo {
    pub fn g() {}
    pub use self::g as f;
}

use foo::*; // This breaks, since the imported re-export conflicts with the following item.
fn f() {}

The breakage can be fixed by renaming the non-import item or by using single imports in place of the glob import.
r? @nrc

[nrc]

cc @rust-lang/lang

[retep998]

Per my other comment here a crater run wouldn't notice breakages to projects that glob import winapi.

[petrochenkov]

Yeah, the breakage looks bad (still would be interested to see crater results).

[bors]

☔️ The latest upstream changes (presumably #31461) made this pull request unmergeable. Please resolve the merge conflicts.

[jseyfried]

rebased

[nikomatsakis]

Since we decided not to "fix" the current behavior, I believe this PR should be closed. Correct me if I am mistaken.