Lua API: implicitly clear animator after playing it (#3536)

This prevents the animator from holding a strong reference to the target unit, which was keeping the unit object alive and thus preventing the unit halo, if any, from disappearing.

(cherry-picked from commit 7d6e2b2a10a61e1704c38ea7ee6aa34178a29b38)

data/lua/wml/animate_unit.lua

@@ -110,5 +110,4 @@ function wesnoth.wml_actions.animate_unit(cfg)
 	local anim = wesnoth.create_animator()
 	add_animation(anim, cfg)
 	anim:run()
-	anim:clear()
-end
+end

data/lua/wml/heal_unit.lua

@@ -44,7 +44,6 @@ function wesnoth.wml_actions.heal_unit(cfg)
 				animator:add(healers[1], 'healing', 'hit', {value = heal_amount})
 			end
 			animator:run()
-			animator:clear()
 		end
 
 		u.hitpoints = new_hitpoints

data/lua/wml/kill.lua

@@ -71,7 +71,6 @@ function wesnoth.wml_actions.kill(cfg)
 				anim:add(secondary_unit, "victory", "kill", {primary = secondary, secondary = primary})
 			end
 			anim:run()
-			anim:clear()
 		end
 		-- wesnoth.wml_actions.redraw{}
 

src/scripting/game_lua_kernel.cpp

@@ -448,6 +448,7 @@ static int impl_run_animation(lua_State* L)
 	anim.start_animations();
 	anim.wait_for_end();
 	anim.set_all_standing();
+	anim.clear();
 	return 0;
 }