This simplifies the logging system.
This also fixes some lost messages on startup.
The simplification is simple. I removed unused functions and moved most things in the .h to the .cpp. I replaced the unnecessary linked list with its contents laid out as three member variables. Anything that went through the linked list now directly accesses the backends. Generic functions are replaced with those for each specific use case and there aren't many. This change increases coupling but we gain back more KISS and encapsulation.
With those changes it was easy to make it thread-safe. I just removed the mutex and turned a boolean atomic. I was planning to use this thread-safety in my next PR about stacktraces. It was actually async-signal-safety at first but I ended up using a different approach. Anyway getting rid of the linked list is important for that because have the list of backends constantly changing complicates things.
This was mainly used to keep track of mapped buffers for later unmapping. Since unmap is no longer implemented, this no longer seves a valuable purpose.
Skip unmapping nvdec buffers to avoid breaking the continuity of the VP9 reference frame addresses, and the risk of invalidating data before the async GPU thread is done with it.
This setting is best referred to as a speed limit, as it involves the limits of all timing based aspects of the emulator, not only framerate.
This allows us to differentiate it from the fps unlocker setting.
GLASM is getting good enough that we can move it out of advanced
graphics settings. This removes the setting `use_assembly_shaders`,
opting for a enum class `shader_backend`. This comes with the benefits
that it is extensible for additional shader backends besides GLSL and
GLASM, and this will work better with a QComboBox.
Qt removes the related assembly shader setting from the Advanced
Graphics section and places it as a new QComboBox in the API Settings
group. This will replace the Vulkan device selector when OpenGL is
selected.
Additionally, mark all of the custom anisotropic filtering settings as
"WILL BREAK THINGS", as that is the case with a select few games.
