Auto merge of #41368 - nikomatsakis:incr-comp-dep-tracking-map, r=eddyb

Auto merge of #41368 - nikomatsakis:incr-comp-dep-tracking-map, r=eddyb

make *most* maps private

Currently we access the `DepTrackingMap` fields directly rather than using the query accessors. This seems bad. This branch removes several such uses, but not all, and extends the macro so that queries can hide their maps (so we can prevent regressions). The extension to the macro is kind of ugly :/ but couldn't find a simple way to do it otherwise (I guess I could use a nested macro...). Anyway I figure it's only temporary.

r? @eddyb