Added nullable to most Content.Shared files (#3238)

* Add nullable to some Content.Shared files.

* Use [NotNullWhen(true)]

* Undo adding now redundant !'s

* Forgot one

* Add a ton more nullable

* You can guess

* Fix some issues

* It actually compiles now

* Auto stash before merge of "null2" and "origin/master"

* I lied

* enable annotations -> enable

* Revert ActionBlockerSystem.cs to original

* Fix ActionBlockerSystem.cs

* More nullable

* Undo some added exclamation marks

* Fix issues

* Update Content.Shared/Maps/ContentTileDefinition.cs

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

* Resolve some issues

* Remove unused method

* Fix more issues

* Fix more issues

* Fix more issues

* Fix more issues

* Fix issue, rollback SharedGhostComponent.cs

* Update submodule

* Fix issue, invert some if-statements to reduce nesting

* Revert RobustToolbox

* FIx things broken by merge

* Some fixes

- Replaced with string.Empty
- Remove some exclamation marks
- Revert file

* Some fixes

* Trivial #nullable enable

* Fix null ables

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>
Co-authored-by: Metal Gear Sloth <metalgearsloth@gmail.com>

Content.Shared/Utility/ContentHelpers.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 
 namespace Content.Shared.Utility
 {

Content.Shared/Utility/Cooldowns.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using Robust.Shared.IoC;
 using Robust.Shared.Timing;
 
@@ -13,14 +14,14 @@ namespace Content.Shared.Utility
         /// <returns>a cooldown interval starting at GameTiming.Curtime and ending at (offset) from CurTime.
         /// For example, passing TimeSpan.FromSeconds(5) will create an interval
         /// from now to 5 seconds from now.</returns>
-        public static (TimeSpan start, TimeSpan end) FromNow(TimeSpan offset, IGameTiming gameTiming = null)
+        public static (TimeSpan start, TimeSpan end) FromNow(TimeSpan offset, IGameTiming? gameTiming = null)
         {
             var now = (gameTiming ?? IoCManager.Resolve<IGameTiming>()).CurTime;
             return (now, now + offset);
         }
 
         /// <see cref="FromNow"/>
-        public static (TimeSpan start, TimeSpan end) SecondsFromNow(double seconds, IGameTiming gameTiming = null)
+        public static (TimeSpan start, TimeSpan end) SecondsFromNow(double seconds, IGameTiming? gameTiming = null)
         {
             return FromNow(TimeSpan.FromSeconds(seconds), gameTiming);
         }

Content.Shared/Utility/SharedDirectionExtensions.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+#nullable enable
+using System.Collections.Generic;
 using Content.Shared.Maps;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;

Content.Shared/Utility/SharedEntityExtensions.cs

@@ -1,4 +1,5 @@
-using System;
+#nullable enable
+using System;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;

Content.Shared/Utility/TemperatureHelpers.cs

@@ -1,4 +1,5 @@
-using Content.Shared.Maths;
+#nullable enable
+using Content.Shared.Maths;
 
 namespace Content.Shared.Utility
 {

Content.Shared/Utility/TransformExtensions.cs

@@ -1,4 +1,5 @@
-using Robust.Shared.GameObjects;
+#nullable enable
+using Robust.Shared.GameObjects;
 
 namespace Content.Shared.Utility
 {