REQ: Make hud_fps_drop follow cl_maxfps

[Matrix-QW]

Is your feature request related to a problem? Please describe.
When I change fps I also need to change the drop variable.

Describe the solution you'd like
Add hud_fps_drop_follow.
When cl_maxfps changes, it would check if 'follow' is enabled and set hud_fps_drop = cl_maxfps -1 (or else fps keep appearing).
If we want 'drop' to use a lower value, just keep 'follow' disabled.

Additional context
For cl_maxfps 1155, set hud_fps_drop 1154.