Strip _xlfn. and _xlfs. In Formula Translations

Fix #3819. Excel can add these prefixes (basically invisible to end-user). Formula translation in PhpSpreadsheet fails when dealing with these unexpected prefixes, and, even if it handled it correctly, the unexpected prefixes confuse the users. I have changed to strip those prefixes when translating to a locale. This is probably not perfect, but is almost certainly good enough. I could easily add the same change when translating from a locale to English, but I don't think there's a good use case for that, so am opting not to do so for now.

The documentation mentions `translateFormulaToLocale` and `translateFormulaToEnglish`. Neither of these exist; both names are preceded by an underscore. I have changed the code to match the documentation rather than vice versa, retaining deprecated versions of the underscored routines which merely invoke the non-underscored routines.

tests/PhpSpreadsheetTests/Calculation/TranslationTest.php

@@ -47,7 +47,7 @@ class TranslationTest extends TestCase
         self::assertSame($expectedResult, $translatedFormula);
 
         $restoredFormula = Calculation::getInstance()->_translateFormulaToEnglish($translatedFormula);
-        self::assertSame($formula, $restoredFormula);
+        self::assertSame(preg_replace('/_(xlfn|xlws)[.]/', '', $formula), $restoredFormula);
     }
 
     public static function providerTranslations(): array