Fully implemented ConVar class so we could statically construct all SDK convars, this avoids a level of indirection, and allows for creating ConVar's everywhere in the project.
This patch also removed the settings tab of the ImGui server browser, as it has threading issues, while it technically never caused a crash yet, it has been removed as there was no point keeping it vs the work required to make it thread save (it only managed 2 convars which are perfectly manageable through cfg's or the in-game console).
Also temporarily disabled the creation of ConVar's in the mod system due to a memory leak, we would allocate and register a convar based on details parsed out of a mod file definition, but never unregister and free it.
Some parts of the engine have to be rebuild in order to implement this correctly, therefore, it has been removed for now to avoid potential performance problems.
fps_max_rt and fps_max_gfx have been limited to 295 to avoid a contest with the engine's hard limit causing huge performance hits.
Limits frames at a much higher level of precision than 'fps_max' and 'fps_max_gfx', probably ideal to reduce input latency even more. Also changed the logic of the NVIDIA Reflex frame limiter, to which it would use the desktop's refresh rate if set to '-1'. The new render thread frame limiter has a similar behavior. Using desktop refresh rates on the render thread or NVIDIA Reflex frame limiter requires 'fps_max' to be set to 0 (unlimited), as it would otherwise result in a major performance drop due to a contest if fps_max_(gfx/rt) is set to a similar number as fps_max.
