More flags on instances to allow more freedom on which instance cast under certains conditions

[walt253]

~~Adds 2 new properties for instance on creature.cfg:~~

~~OUT_OF_BATTLE allows instance to be used whenever available when the creature is not fighting and not imprisoned.~~ ~~WHILE_IMPRISONED allows instance to be used whenever available when the creature is imprisoned.~~

EDIT: it now adds a whole bunch of Activation Flag instead. See comments on creature.cfg.

[walt253]

Last commit description isn't clear, what I meant is when you give only OUT_OF_BATTLE to an instance then it shouldn't be used during a combat.

[walt253]

Tried to move stuff to the header but it didn't work either so for now back to using a number for func_idx check because of build warnings/errors that I can't figure why it happens 🥲. If someone know why and know how to fix, please go ahead and fix it, if you want of course, thanks!

[Loobinex]

Since walter is having discord issues, this was the final state of this PR: