Rider static analysis (#433)

* Non-accessed local variable

* Merge cast and type checks.

* StringComparison.Ordinal added for better culture support

* Supposed code improvement in launcher. Remove unused code.

* Update ExplosionHelper.cs

Unintentional change.

* Optimized Import

* Add Robust.Shared.Utility import where it was deleted

* Other random suggestion

* Improve my comment

Content.IntegrationTests/StartTest.cs

@@ -1,7 +1,6 @@
 using System.Threading.Tasks;
 using NUnit.Framework;
 using Robust.Shared.Exceptions;
-using Robust.UnitTesting;
 
 namespace Content.IntegrationTests
 {