Misc performance tweaks (#4509)

* use Array.Empty() where instead of allocating new zero-length arrays

* structure for loops in a way that the JIT will elide array/Span bounds checking

* avoiding function calls in for loop condition tests

* avoid LINQ in a hot path

* conform with code style

* fix mistake in GetNextWaitingObject()

* fix GetNextWaitingObject() possibility of returning null if all list items have TimePoint == long.MaxValue

* make GetNextWaitingObject() behave FIFO behavior for multiple items with the same TimePoint

ARMeilleure/CodeGen/Arm64/CodeGenContext.cs

@@ -265,7 +265,7 @@ namespace ARMeilleure.CodeGen.Arm64
             }
             else
             {
-                relocInfo = new RelocInfo(new RelocEntry[0]);
+                relocInfo = new RelocInfo(Array.Empty<RelocEntry>());
             }
 
             return (code, relocInfo);