The Big Legion Makeover: Amputator Added

[ZephyrSkies7]

Work done

Replaced the Cortex Agitator with a new, cluster bombardment artillery turret dubbed the Amputator.

Addresses Issue(s)

Replaces placeholder Cortex tier 1 static artillery defence with original Legion unit.

Needs Fixing

• The Legion wreck texture atlas, as well as damage shader, needs to be fixed before this unit is ready to add to the game.
• The unit still needs to be balanced properly by Zecrus before this unit is ready to add to the game.
• The unit's script is still being worked on by @efrec, it will be added in a future commit once it's finished. It is temporarily using a triple burst plasma barrage (way too OP, just for testing purposes).

Screenshots:

[ZephyrSkies7]

Merged in #2999