- Prevents a cloned session's handler from being overwritten by another disconnected session.
- Fixes session handler nullptr asserts with Pokemon Sword & Shield.
- Previously, we would allocate a thread per session, which adds new threads on CloneCurrentObject.
- This results in race conditions with N sessions queuing requests to the same service interface.
- Fixes Pokken Tournament DX crashes/softlocks, which were regressed by #6347.
Over the course of the kernel refactoring a tiny bit of missing
overrides slipped through review, so we can add these.
While we're at it, we can remove redundant virtual keywords where
applicable as well.
