Code Cleanup: Integration Tests (#29584)

* Cleanup PuddleTest

* Cleanup GravityGridTest

* Cleanup PowerTest

* Cleanup SaveLoadMapTest

* Cleanup Body tests

* Cleanup ContainerOcclusionTest

* Cleanup AirlockTest

* Cleanup DamageableTest

* Cleanup EntityTest

* Cleanup FluidSpillTest

* Cleanup FollowerSystemTest

* Cleanup HandCuffTest

* Cleanup InteractionSystemTests

* Cleanup InRangeUnobstructed

* Cleanup SimplePredictReconcileTest

* Cleanup PostMapInitTest

* Cleanup SalvageTest

* Cleanup SaveLoadSaveTest

* Cleanup ShuttleTest

* Cleanup MaterialArbitrageTest

* Cleanup PrototypeSaveTest

* Fix ShuttleTest

* Bunch of small ones

* Move JobTests to Station directory

* More small fixes

* Cleanup InteractionTest.Helpers
Had to change a method signature, so some callers were modified too.

* Missed one

Content.IntegrationTests/Tests/SalvageTest.cs

@@ -1,5 +1,4 @@
 using System.Linq;
-using Content.Server.Salvage;
 using Content.Shared.CCVar;
 using Content.Shared.Salvage;
 using Robust.Server.GameObjects;
@@ -28,6 +27,7 @@ public sealed class SalvageTest
         var mapManager = server.ResolveDependency<IMapManager>();
         var prototypeManager = server.ResolveDependency<IPrototypeManager>();
         var cfg = server.ResolveDependency<IConfigurationManager>();
+        var mapSystem = entManager.System<SharedMapSystem>();
         Assert.That(cfg.GetCVar(CCVars.GridFill), Is.False);
 
         await server.WaitPost(() =>
@@ -36,7 +36,7 @@ public sealed class SalvageTest
             {
                 var mapFile = salvage.MapPath;
 
-                var mapId = mapManager.CreateMap();
+                mapSystem.CreateMap(out var mapId);
                 try
                 {
                     Assert.That(mapLoader.TryLoad(mapId, mapFile.ToString(), out var roots));