Improve renderer/network isolation and add fixed net fps cvar

[AltimorTASDK]

No description provided.

[j4reporting]

this introduces at least two regressions that I am aware of

1. the lift in rm_resurgence ( re:Mobilize 1.2b ) from level 0 to level 1 in the Trident buildung will revert its direction before reaching level 1 (also from level B to level 0 later in the game) level 1 to level 2 and level 2 to level 3 are not affected . I'll attach a savegame.

2. lifts/ platforms in peril mod will block and player is taking damage at the same time
   w/o this PR lift (at the start of the map) will work with vsync enabled

savegame-rm_resurgence.zip