save-analysis: emit names of items that a glob import actually imports.

There is also some work here to make resolve a bit more stable - it no longer overwrites a specific import with a glob import.
auto merge of #19254 : nick29581/rust/dxr-glob, r=pcwalton

There is also some work here to make resolve a bit more stable - it no longer overwrites a specific import with a glob import.

r?