Moves render target restoring to RestoreAPIState, this also means no need
to manually restore after allocating in a buffer that caused execution,
because the manager restores it for us.
Remove a method that wasn't used from D3DUtil.cpp, and fixes a few errors
in EFB poke drawing.
A few StreamBuffer instances take arguments that are actually size_t,
and this will cause truncation warnings during argument forwarding
with make_unique.
