Include import name in import shadowing error messages.

This partially alleviates the confusing behavior in issue #16597
Update compile-fail tests due to changed diagnostics
Add compile-fail test for missing import shadowing case
Register new snapshots
test: Ignore a deadlocking test on OSX

This test apparently keeps making no progress and timing out builds on the OSX
builder, so this commit is switching the test to be ignored.

cc #16872
auto merge of #16598 : bkoropoff/rust/import-shadow-name, r=alexcrichton

This partially alleviates the confusing behavior in issue #16597
auto merge of #16859 : alexcrichton/rust/snapshots, r=huonw
auto merge of #16873 : alexcrichton/rust/ignore-deadlocks, r=sfackler

This test apparently keeps making no progress and timing out builds on the OSX
builder, so this commit is switching the test to be ignored.

cc #16872