add GetUnitPhysicalState for lua

[loveridge]

For https://github.com/beyond-all-reason/spring/issues/1520 Can be used to determine if a unit has any of the following:

enum PhysicalState {
    PSTATE_BIT_ONGROUND    = (1 << 0),
    PSTATE_BIT_INWATER     = (1 << 1),
    PSTATE_BIT_UNDERWATER  = (1 << 2),
    PSTATE_BIT_UNDERGROUND = (1 << 3),
    PSTATE_BIT_INAIR       = (1 << 4),
    PSTATE_BIT_INVOID      = (1 << 5),

    PSTATE_BIT_MOVING   = (1 <<  6),
    PSTATE_BIT_FLYING   = (1 <<  7),
    PSTATE_BIT_FALLING  = (1 <<  8),
    PSTATE_BIT_SKIDDING = (1 <<  9),
    PSTATE_BIT_CRASHING = (1 << 10),
    PSTATE_BIT_BLOCKING = (1 << 11),
};

[WatchTheFort]

How does this handle impossible states, like something being both in air and underwater at the same time? Or is it up to games to say for themselves what an impossible state is?

[sprunk]

If you set an impossible state via lua, the getter will just regurgitate it. Engine resets the state each simframe and will never produce something impossible.

[WatchTheFort]

I don't understand... you can set state via Lua, but the engine resets it every frame? Isn't that the same as not being able to set state from Lua?

[sprunk]

There's 2 kinds of bits in the physical state:

• those that are a derivative of something else (for example "is in water" is based on the underlying "y < 0"). Setting those via Lua is largely useless and will go back to reflecting the underlying value on the next simframe but could still have an effect if later-layer Lua were to look at the bits instead of the underlying thing (think dota slardar puddle setting the river bit).
• those that represent a fundamental state themselves (for example "is skidding"). Setting those bits is useful because it is supposed to put the unit into the relevant state, which should generally linger around until the unit fulfils the conditions to be put into another state. An impossible state (e.g. if you set both skidding and flying) is supposed to get resolved into one of them.