Merge #7336

7336: Rename `CrateDefMap` to `DefMap` r=matklad a=jonas-schievink

I propose handling local items by computing a `DefMap` for every block expression, using the regular (early) name resolution algorithm. The result of that will be a `DefMap` that has a reference to the parent `DefMap`, which is either the one computed for the containing block expression, or the crate's root `DefMap`. Name resolution will fall back to a name in the parent `DefMap` if it cannot be resolved in the inner block.

The `DefMap`s computed for block expressions will go through a separate query that can be garbage-collected much more aggressively, since these `DefMap`s should be cheap to compute and are never part of a crate's public API.

The first step towards that is to make `CrateDefMap` not specific to crates anymore, hence this rename (if this plans sounds reasonable).

cc https://github.com/rust-analyzer/rust-analyzer/issues/7325 and https://github.com/rust-analyzer/rust-analyzer/issues/1165

Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>