Allow Stun Lance to target Mind Controlled units

[copyrite]

Fixes #1312

[Iridar]

Not 100% comfortable changing a function that could be potentially getting used by mods to create their own versions of Stun Lance where the changed behavior may or may not be necessary. This change is on the edge between a bugfix and a BC break.

OTOH TreatMindControlledSquadmateAsHostile is a really weird flag you would expect to be true by default.

[Iridar]

Please add an empty line after this.

[copyrite]

I expect this PR to have the same merge conflict as #1313, the project file changes all landed on the same line in alphabetical order. Therefore I'd wait for that one to be merged first.

[copyrite]

I'll also repeat here the consideration I brought up on Discord:

I'm not completely sure if there's a mod compatibility risk related to AI. For example, let's say there's a Sectoid and Stun Lancer in play. Sectoid Mind Controls an XCOM soldier. Before the fix, the same XCOM soldier is not a valid target for Stun Lance, but after the fix, it is.

Testing this in a vanilla game both with and without highlander, and verifying the available moves with x2allowselectall, I found that the Lancer will not attack the mind controlled target even if it has the option to do so. But if this feels like it'd cause unwanted changes downstream, I'm not bummed if this PR gets rejected. After all the situation where the player would get burnt by this interaction is very niche; take 2 MCs (one of which is a Lancer) and make them fight against each other.