Auto merge of #53711 - arielb1:macro-table, r=michaelwoerister
create a valid DefIdTable for proc macro crates
At least the incremental compilation code, and a few other places in the
compiler, require the CrateMetadata for a loaded target crate to contain a
valid DefIdTable for the DefIds in the target.
Previously, the CrateMetadata for a proc macro contained the crate's
"host" DefIdTable, which is of course incompatible with the "target"
DefIdTable, causing ICEs. This creates a DefIdTable that properly refers
to the "proc macro" DefIds.
Fixes #49482.
r? @michaelwoerister
Should we beta-nominate this?