Waterbox supports threads now, but they're not real threads on the host side because that's complicated and can be nondeterministic. Instead, everything is scheduled to share one host thread. This means that scheduling is actually cooperative and certain patterns of spinlocks and other nonsense can fail to work at all, but "regular" code probably will.
With this, add DobieStation PS2 core. This core was selected because it has threads and is otherwise simple to port; easy to build and a good core/frontend separation. It's not a wonderful core however, with low speed (made abysmally lower by our lack of real threads) and low compatibility, so it remains a curiosity for now.
This broke any waterbox core that called in to native code in the same EnterExit() right after sealing. All nyma cores were broken, 32x was not, didn't check the rest. Regressed in 175556529e.
It worked fine in release mode, theoretically
Set up a second mirror of guest memory; easily accomplished because we were already using memfd_create / CreateFileMappingW.
This lets us simplify a lot of host code that has to access guest memory that may not be active right now, or might have been mprotect()ed to something weird. Activate is only needed now to run guest code, or when the C# side wants to peer into guest memory for memory domains and such (waterboxhost does not share the mirror address with the C# side).
Waterbox guest code now runs on a stack inside the guest memory space. This removes some potential opportunities for nondeterminism and makes future porting of libco-enabled cores easier.
This replaces the old managed one. The only direct effect of this is to fix some hard to reproduce crashes in bsnes.
In the long run, we'll use this new code to help build more waterbox features.
bigbass1997