Auto merge of #33473 - michaelwoerister:split-cratecontext, r=nikomatsakis

Preparatory refactorings for collector-driven trans.

This is a set of refactorings that allows to do translation item collection and partitioning before LocalCrateContext instances or LLVM modules are generated. As a consequence we can now create LocalCrateContexts already with knowledge of the codegen unit it will be used for. This is a preparation step for driving trans by the results of codegen unit partitioning.

diff --cc src/librustc_trans/base.rs
Simple merge

diff --cc src/librustc_trans/common.rs
Simple merge