Repeated calculation of the same angle in FindValidPositionByFan results in a little resource waste

the bird book will summon 21-30 birds(at first time), call FindValidPositionByFan(start_angle, radius, attempts=12, test_fn) many times.
and the local table "angles" is same when "attempts" is not changed. so cache the result will save a little resource.
my example patch is attched.

cacheFanAngles.patch