Extract all Base Conversion functions from the Engineering class into…

… dedicated Base Conversion classes (#1849)

* Extract all Base Conversion functions from the Engineering class into a dedicated Convert<Base> classes extending from a common ConvertBase class

Retain the original methods in the Engineering class as stubs for BC, but deprecate them. They will be removed for PHPSpreadsheet v2

Note that unit tests still point to the Engineering class stubs; these should be modified to use the Convert<Base> classes directly when the stubs are removed

* Split out into separate base conversion classes, with a ConvertBase class for common methods

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -403,17 +403,17 @@ class Calculation
         ],
         'BIN2DEC' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'BINTODEC'],
+            'functionCall' => [Engineering\ConvertBinary::class, 'toDecimal'],
             'argumentCount' => '1',
         ],
         'BIN2HEX' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'BINTOHEX'],
+            'functionCall' => [Engineering\ConvertBinary::class, 'toHex'],
             'argumentCount' => '1,2',
         ],
         'BIN2OCT' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'BINTOOCT'],
+            'functionCall' => [Engineering\ConvertBinary::class, 'toOctal'],
             'argumentCount' => '1,2',
         ],
         'BINOMDIST' => [
@@ -814,17 +814,17 @@ class Calculation
         ],
         'DEC2BIN' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'DECTOBIN'],
+            'functionCall' => [Engineering\ConvertDecimal::class, 'toBinary'],
             'argumentCount' => '1,2',
         ],
         'DEC2HEX' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'DECTOHEX'],
+            'functionCall' => [Engineering\ConvertDecimal::class, 'toHex'],
             'argumentCount' => '1,2',
         ],
         'DEC2OCT' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'DECTOOCT'],
+            'functionCall' => [Engineering\ConvertDecimal::class, 'toOctal'],
             'argumentCount' => '1,2',
         ],
         'DECIMAL' => [
@@ -1216,17 +1216,17 @@ class Calculation
         ],
         'HEX2BIN' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'HEXTOBIN'],
+            'functionCall' => [Engineering\ConvertHex::class, 'toBinary'],
             'argumentCount' => '1,2',
         ],
         'HEX2DEC' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'HEXTODEC'],
+            'functionCall' => [Engineering\ConvertHex::class, 'toDecimal'],
             'argumentCount' => '1',
         ],
         'HEX2OCT' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'HEXTOOCT'],
+            'functionCall' => [Engineering\ConvertHex::class, 'toOctal'],
             'argumentCount' => '1,2',
         ],
         'HLOOKUP' => [
@@ -1840,17 +1840,17 @@ class Calculation
         ],
         'OCT2BIN' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'OCTTOBIN'],
+            'functionCall' => [Engineering\ConvertOctal::class, 'toBinary'],
             'argumentCount' => '1,2',
         ],
         'OCT2DEC' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'OCTTODEC'],
+            'functionCall' => [Engineering\ConvertOctal::class, 'toDecimal'],
             'argumentCount' => '1',
         ],
         'OCT2HEX' => [
             'category' => Category::CATEGORY_ENGINEERING,
-            'functionCall' => [Engineering::class, 'OCTTOHEX'],
+            'functionCall' => [Engineering\ConvertOctal::class, 'toHex'],
             'argumentCount' => '1,2',
         ],
         'ODD' => [