Make all test methods static

Author: xoofx

src/Unity.Mathematics.CodeGen/VectorGenerator.cs

@@ -1884,7 +1884,7 @@ void GenerateSwizzles(int[] swizzle, StringBuilder str)
         private void BeginTest(StringBuilder str, string name)
         {
             str.Append("\t\t[TestCompiler]\n");
-            str.AppendFormat("\t\tpublic void {0}()\n", name);
+            str.AppendFormat("\t\tpublic static void {0}()\n", name);
             str.Append("\t\t{\n");
         }