Handle threat/detection per group.

Some SAMs have multiple groups (such as an SA-10 group with its
accompanying SA-15 and SA-19 groups). This shows each group's threat and
detection separately on the map, and also makes it so that an SA-10 with
dead radars will no longer contribute to the threat zone just because
the shilka next to it still has a functioning radar.

https://github.com/Khopa/dcs_liberation/issues/647
Fixes https://github.com/Khopa/dcs_liberation/issues/672

changelog.md

@@ -15,6 +15,7 @@ Saves from 2.3 are not compatible with 2.4.
 * **[Balance]** Opfor now gains income using the same rules as the player, significantly increasing their income relative to the player for most campaigns.
 * **[Economy]** FOBs generate only $10M per turn (previously $20M like airbases).
 * **[Economy]** Carriers and off-map spawns generate no income (previously $20M like airbases).
+* **[UI]** Multi-SAM objectives now show threat and detection rings per group.
 
 # 2.3.3