This refactors the ship registry and the OSWPT struct to store data as indexes rather than pointers. This is a prerequisite for making these collections dynamic in the future. See also #5800.
In many calls to `ship_get_subsystem_strength`, the caller doesn't care about the actual number, just whether the subsystem type is destroyed. So this adds an optimization to check specifically for that. In the case of `SUBSYSTEM_ENGINE`, this avoids an iteration over every subsystem on the ship which, for a ship with many turrets, can be significant.
Add "tactical" versions of disable and disarm goals which only perform the specific task without implying anything else. The target ship is not protected and attack goals are not cleared from other ships.
There is also a new AI profiles flag to make this the default hud squad message command instead of the classic disable/disarm.
The ai-fly-to-ship goal was added early in FSO's development but never worked right. Until recently it could crash; and even aside from the crash the AI would try to reach the target's exact position, causing repeated collisions. This folds ai-fly-to-ship into ai-stay-near-ship, since the behaviors are conceptually the same except for fly-to being satisfied as soon as the target is in range.
This also adds a new "escort" mode usable by both behaviors. The default Volition behavior is to swoop toward the target in a long, graceful arc; the new mode generates a goal point and flies directly to that point. These can be toggled via an optional sexp parameter.
There is also some minor cleanup and a new vec3d operator for convenience.
Needed for Scroll; depends on #5667.
Adds a `DEATH_ROLL` status to specifically cover the state after ships have been destroyed but before they exit. I've also audited all code that interacts with the ship registry to use the correct state with this new state taken into consideration.
This fixes access to exploding ships that was broken when the ship registry framework was introduced. In particular, the `when destroyed X beam-lock-all X` QoL feature now works again.
When only one AI class performs autoscaling, the math formulas which use autoscaling will become meaningless (e.g. in `ai_maybe_launch_cmeasure()`) or will cause divide-by-zero errors (e.g. in `ai_manage_shield()`). And autoscaling is not very useful outside of the specific ways that Volition used it. So this adds some warnings and disables single-occurrence autoscaling.
Fixes#5474.
Goober5000