Only allow vertical view shifting when 3D FOV is enabled

[kevingranade]

Summary

SUMMARY: Bugfixes "Close exploit that allowed peeking through floors and ceilings."

Purpose of change

Fixes #30300
Basically reverts #34075
We accidentally enabled shifting the game point of view when 3D FOV was disabled, which can not possibly provide correct behaviour. The result was that when shifting the view to a different z-level, the map would be drawn as if the player were at that location, even if that location is unreachable for the player.

Describe the solution

Check the 3D_FOV option in the two places where this shifting occurred, and if it is not true, do not allow shifting.

Testing

The two use cases I'm aware of were invoking "look around", bound by default to ';' and then using '<' or '>' to shift the level, or entering the aim menu, bound by default to 'f' (when wielding a ranged weapon), and then invoking "look up" or "look down", which are not bound by default.

Alternatives

Instead of disabling look up/look down, it might be beneficial to enable the feature, but not run FOV on the new map level, instead clearing it so that the game can at least display map memory for previously visited areas.

Additional context

There is no need to try to extend this functionality to be usable when 3D FOV is disabled, this kind of thing is exactly why 3D FOV needs to exist.