race: add new settings to control vehicle physics behavior

[xLive]

This PR adds new settings that can be configured globally by the server or per map to control vehicle physics behavior. By default, they do not change the current behavior unless set in race or map settings. These settings were added to fix issues caused by multitheftauto/mtasa-blue#4243, which broke many custom maps and made them unfinishable. They allow server owners and mappers to bring back the old physics on specific maps by disabling the fix and setting the FPS those maps were designed for, without affecting other maps. The old behavior can also be enabled globally.

New settings:

• vehicle_physics_mode
  Controls physics behavior. fixed for FPS-independent physics, or legacy to restore the old behavior. Default is fixed.
• vehicle_physics_fps
  Sets the FPS limit when vehicle_physics_mode is set to legacy. -1 to keep the current limit, or set a specific FPS value. The original FPS limit is restored when the map or race resource stops. Default is -1.
• vehicle_physics_mode_map_can_override and vehicle_physics_fps_map_can_override
  Allow maps to override the global vehicle_physics_mode and vehicle_physics_fps values. Default is true.

[Dutchman101]

This is my proposal for a perfect design:

• If a racing map has no physics (legacy or fixed) flag in meta.xml / Map settings, default to legacy. So that old maps need no intervention to provide the same experience as which they were designed for.
• When a racing map starts that has a specific physics flag in meta.xml / Map settings, apply it accordingly.
• Make sure that if "race" gamemode stops, it restores the glitch state to what it was when "race" loaded, or what it was before the first map that "race" decided a physics setting for (based on the map properties).

So then, racing servers only need to update mtasa-resources when MTA 1.7 releases in the coming few weeks, something that has been stressed with every new release anyways.
@xLive

[xLive]

This is my proposal for a perfect design:

• If a racing map has no physics (legacy or fixed) flag in meta.xml / Map settings, default to legacy. So that old maps need no intervention to provide the same experience as which they were designed for.

When a racing map hasn’t set the physics mode, it will use whatever the server has set in the race resource settings. By default, it was fixed, but I’ve now changed it to legacy.

• When a racing map starts that has a specific physics flag in meta.xml / Map settings, apply it accordingly.
• Make sure that if "race" gamemode stops, it restores the glitch state to what it was when "race" loaded, or what it was before the first map that "race" decided a physics setting for (based on the map properties).

The PR already does both of these. It applies the new settings based on what each map has in its meta settings. If the map hasn’t set anything, it uses the values from the race resource settings. It also restores the glitch state when the race resource stops.

Side note: I suggest we use fixed physics mode for the default race maps to benefit from the physics fix. From quick testing on several maps, it’s very unlikely they will be broken by fixed mode. If that’s okay, I will change them in a future PR.