[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.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@302965 91177308-0d34-0410-b5e6-96231b3b80d8