Almost all the virtual functions in Renderer are part of dolphin's
"graphics api abstraction layer", which has slowly formed over the
last decade or two.
Most of the work was done previously with the introduction of the
various "AbstractX" classes, associated with texture cache cleanups
and implementation of newer graphics APIs (Direct3D 12, Vulkan, Metal).
We are simply taking the last step and yeeting these functions out
of Renderer.
This "AbstractGfx" class is now completely agnostic of any details
from the flipper/hollywood GPU we are emulating, though somewhat
specialized.
(Will not build, this commit only contains changes outside VideoBackends)
Fixes incorrect logspam when the buffer needed to be reset on flushes (which we already were doing, but 52feed04db moved it to after the check was made). This is https://bugs.dolphin-emu.org/issues/10312.
I also converted it to an assert, as if this does happen, things are going to render incorrectly, so we want to make it obvious.
Rather than makring some parts of VertexLoaderManager dirty in some places and some in others, do it all in VideoState. Also, since CPState no longer contains pointers/non-CP data after d039b1bc0d, we can just use p.Do on it instead of manually saving each field.
This more accurately represents what's going on, and also ends at 0 instead of 1, making some indexing operations easier. This also changes it so that position_matrix_index_cache actually starts from index 0 instead of index 1.
