Fixes a bug that occurs when:
- `CoInitializeEx(NULL, COINIT_MULTITHREADED);` is called on thread 1 - `CoInitializeEx(NULL, COINIT_MULTITHREADED);` is called on thread 2 - `CoUninitialize()` is called on thread 1. - `CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);` is called on thread 1.
After this, when attempting to marshal an interface on thread 2, when `ipid_to_ifstub` is called, `apartment_findfromtid()` will find thread 1's STA and not the MTA.
-- v2: combase: Omit thread ID from the stub manager ipid for MTA objects.