Ungarrison units in the direction of their garrisonholders rallypoint

[Imarok]

When the initial spawnpoint of a building is unconnected with the rest of the map, you won't be able to use the units from this building, because they are trapped inside this unconnected area. This often happens when you build a fortress near some trees and train some rams.

In this picture, we see a catapult being trained, but it's trapped inside some trees, because it spawns at the initial spawnpoint of the fortress (red circle):

The solution to this issue is to set the inital spawnpoint at the position, their is in.

refs #4484

[elexis]

Also refs #4713. We might have to do 4713 beforehand, because the Footprint component is slow af and needs a different approach before we add more features (though I guess changing the starting angle wouldn't hurt much).

So I guess the two feature requests should work this way: 1. start at rallypoint 2. if there is no rallypoint, start at the template position.

[mimo]

Concerning this ticket itself, I agree that it may be a bit annoying but still buildings have a door! and it seems logical to start spawning at the door. It's the responsability of the player to position its structure (rotations are really easy to do) in a way that the door is not blocked. Maybe adding a more visible indicator of the door when positionning a foundation would help?

[elexis]

(Not a real solution, but the reported issue could also be avoided from the player side by placing an outpost or house between the trees, or to gather the trees.)

The requested feature might be useful in other situations too. For example if we set a building in a central location and sometimes want to ungarrison and then attack at the left or right side.

mimo's idea works too for me. (Maybe the one who wants to implement it can decide.)

[temple]

In 21144:

Spawn units in rally point direction

Differential Revision: ​https://code.wildfiregames.com/D1041
Reviewed by: bb
Comments by: elexis, wraitii
Fixes: #4735