Unit Converter - Calculate the rounding precision of results based on the source (#498)

* precisely calculates the number of digits of the source and compute the number of significant digits of the result based on that.

* fix unit test

* Fix warning C4267

* Optimize how we calculate the number of digits in the integer part and don't trim the value when used by the currency converter

* modify GetNumberSignificantDigits

* fix CI error

* Access to wstring::npos from static calls

* Move UnitConverter static methods related to number to NumberFormattingUtils

* rename namespace

* Add comment and fix typo

* Move standard headers

src/CalcManager/UnitConverter.h

@@ -279,9 +279,7 @@ namespace UnitConversionManager
         double Convert(double value, ConversionData conversionData);
         std::vector<std::tuple<std::wstring, Unit>> CalculateSuggested();
         void ClearValues();
-        void TrimString(std::wstring& input);
         void InitializeSelectedUnits();
-        std::wstring RoundSignificant(double num, int numSignificant);
         Category StringToCategory(const std::wstring& w);
         std::wstring CategoryToString(const Category& c, const wchar_t* delimiter);
         std::wstring UnitToString(const Unit& u, const wchar_t* delimiter);