Goto Micro AI: prevent potential conflict between Goto MAIs

If several Goto MAIs are used on the same side and both have
unique_goals=yes set, they previously might have interfered with each
other, one preventing the other from working correctly. Now the “goal
taken” information is saved such that it only applies to the CA by
which it was set.
[micro_ai] tag setup: minor code cleanup
Micro AIs other engines: code cleanup