Updating Dragon4 to ensure the number buffer always provides a significant digit if one exists. (#25096)
* Updating Dragon4 to ensure the number buffer always provides a significant digit if one exists.
* Changing System.Number.RoundNumber to not round up floating-point numbers.
* Re-enabling the RealFormatterTestsBase CoreFX tests
* Updating Number.RoundNumber to take a isCorrectlyRounded parameter and to use IEEE compliant rounding for floating-point numbers.
* Change SinglePrecisionCustomFormat to 7, ensuring it matches the value used in netcoreapp2.1