Run a second pass of DetectExitPoints to use 'return;' as exit point if no previous transform picked another exit point.

This eliminates redundant 'return;' and 'yield break;' instructions.

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -109,7 +109,7 @@ namespace ICSharpCode.Decompiler.CSharp
 						)
 					}
 				},
-				//new DetectExitPoints(canIntroduceExitForReturn: true),
+				new DetectExitPoints(canIntroduceExitForReturn: true),
 				new DelegateConstruction(),
 			};
 		}

ICSharpCode.Decompiler/IL/ControlFlow/ExitPoints.cs

@@ -167,6 +167,11 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 
 		private bool CanIntroduceAsExit(ILInstruction inst)
 		{
+			if (currentContainer.LeaveCount > 0) {
+				// if we're re-running on a block container that already has an exit,
+				// we can't introduce any additional exits
+				return false;
+			}
 			if (inst is Leave l && l.IsLeavingFunction) {
 				return canIntroduceExitForReturn;
 			} else {