Convert agActor coordinate functions to use dataclass return types.

The agActor code has numerous function/methods that use a confusing list of return types that isn't well documented. These return values are then used with a single-letter variable name and index access. This is for critical sections of the code and makes reading and changing this code difficult and error prone (and we have lost engineering time due to this very problem with this exact code).

Update the functions/methods to use a dataclass that has explicit names for return values and update the usage of those return values accordingly.