[modules] When creating a declaration, cache its owning module immediately

[modules] When creating a declaration, cache its owning module immediately
rather than waiting until it's queried.

Currently this is only applied to local submodule visibility mode, as we don't
yet allocate storage for the owning module in non-local-visibility modules
compilations.

This reinstates r302965, reverted in r303037, with a fix for the reported
crash, which occurred when reparenting a local declaration to be a child of
a hidden imported declaration (specifically during template instantiation).

llvm-svn: 303224