fix: floating-point number serialization issue for non-normal values

[filzrev]

This PR intended to fix #991.

What's changed in this PR

• Replace formatter.FormatNumber(object value); call to ToString("G", CultureInfo.InvariantCulture).
  • It's required to serialize special symbols (Nan/PositiveInfinite/NegativeInfinite) to JSON compatible string representation.
  • Additionally explicitly specify format (G) to align YAML serialized value
• Remove NumericRegex checks. Instead add IsNaN/IsInfinity checks
• Add unit test code (SerializationOfNumericsAsJsonRountTrip)