Experimental AI: use checked versions of the AI actions

So that only valid actions are executed and useful error messages are
produced if something goes wrong.

data/ai/lua/generic_recruit_engine.lua

@@ -559,7 +559,7 @@ return {
             until recruit_type ~= nil
 
             if wesnoth.unit_types[recruit_type].cost <= wesnoth.sides[wesnoth.current.side].gold then
-                ai.recruit(recruit_type, recruit_data.recruit.best_hex[1], recruit_data.recruit.best_hex[2])
+                AH.checked_recruit(ai, recruit_type, recruit_data.recruit.best_hex[1], recruit_data.recruit.best_hex[2])
 
                 -- If the recruited unit cannot reach the target hex, return it to the pool of targets
                 if recruit_data.recruit.target_hex ~= nil and recruit_data.recruit.target_hex[1] ~= nil then

data/ai/lua/generic_rush_engine.lua

@@ -254,7 +254,7 @@ return {
             if AH.print_exec() then print_time('   Executing castle_switch CA') end
             if AH.show_messages() then W.message { speaker = leader.id, message = 'Switching castles' } end
 
-            ai.move(leader, self.data.leader_target[1], self.data.leader_target[2])
+            AH.checked_move(ai, leader, self.data.leader_target[1], self.data.leader_target[2])
             self.data.leader_target = nil
         end
 
@@ -500,7 +500,7 @@ return {
             -- If several attacks have poison, this will always find the last one
             local is_poisoner, poison_weapon = AH.has_weapon_special(attacker, "poison")
 
-            ai.attack(attacker, defender, poison_weapon)
+            AH.checked_attack(ai, attacker, defender, poison_weapon)
 
             self.data.attack = nil
         end
@@ -606,7 +606,7 @@ return {
             if target then
                 local x, y = wesnoth.find_vacant_tile(target[1], target[2], unit)
                 local dest = AH.next_hop(unit, x, y)
-                ai.move(unit, dest[1], dest[2])
+                AH.checked_move(ai, unit, dest[1], dest[2])
             end
         end
 

data/ai/lua/move_to_any_target.lua

@@ -44,7 +44,7 @@ return {
         end
 
         function move_to_any_target:move_to_enemy_exec()
-            ai.move(self.data.unit, self.data.destination[1], self.data.destination[2])
+            AH.checked_move(ai, self.data.unit, self.data.destination[1], self.data.destination[2])
         end
 
         return move_to_any_target