Micro AIs: split up Animals MAI engine file

... into a separate file for each animal AI.  This is a first step
toward separating the animal MAIs, as keeping them together is not
needed any more.
Animals MAIs: get rid of animal_type= key

The previous value of animal_type= now goes directly into ai_type=
Animals MAIs: add syntax translation and deprecation message

So that the ai_type=animals animal_type=... syntax still works for the
time being.
Animals MAIs: add individual engine macros for each AI

... so that only the code for the animal AI used is loaded.
Add deprecation message for MICRO_AI_ANIMALS macro
Swarm MAI test scenario: switch to new animals MAI syntax
Animals MAI test scenario: switch to new animals MAI syntax
Dragon MAI test scenario: switch to new animals MAI syntax
Wolves MAI test scenario: switch to new animals MAI syntax
Big Animals MAI engine: don't load two unused libraries
Wolves MAI engine: don't load unused library file
Animals MAIs: rename internal engine functions and CAs

This shouldn't affect anything else, it is simply done for consistency
(to reflect the recent syntax changes).
Removed a double [filter_attack] in the Skeleton Rider
Micro AIs: split up Guardian MAI engine file

... into a separate file for each animal AI. This is a first step
toward separating the guardian MAIs, as keeping them together is not
needed any more.
Guardian MAIs: get rid of guardian_type= key

The previous value of guardian_type= now goes directly into ai_type=
Guardian MAIs: add syntax translation and deprecation message

So that the ai_type=guardian_unit guardian_type=... syntax still works
for the time being.
Guardian MAIs: add individual engine macros for each AI

... so that only the code for the guardian AI used is loaded.
Add deprecation message for MICRO_AI_GUARDIAN macro
Guardian MAIs: rename internal engine functions and CAs

This shouldn't affect anything else, it is simply done for consistency
(to reflect the recent syntax changes).
Animal MAI engine macros: update ids in the [ai] tags

This doesn't really affect anything, but should be done for consistency
anyway.