Final part of breaking down the Engineering class for Excel Engineering functions into smaller individual/group classes (#1940)

* Final breaking down the Engineering class for Excel Engineering functions into smaller individual/group classes
* Additional unhappy path tests for Complex Number functions
* Fix return docblocks for floats to allow for error strings

tests/data/Calculation/Engineering/COMPLEX.php

@@ -1,5 +1,7 @@
 <?php
 
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+
 return [
     [
         '3+4i',
@@ -14,8 +16,16 @@ return [
         12.34, 5.6699999999999999, 'j',
     ],
     [
-        '#VALUE!',
-        3.5, 'A',
+        Functions::VALUE(),
+        3.5, 'NaN',
+    ],
+    [
+        Functions::VALUE(),
+        'NaN', 3.5,
+    ],
+    [
+        Functions::VALUE(),
+        1.5, 3.5, 'invalid suffix',
     ],
     [
         '1.234E-5+6780000000i',