JSONSerialization: Add missing numeric types
JSONSerialization: Add missing numeric types

- Add support for Int8/Int16/Int32/Int64, UInt8/UInt16/UInt32/UInt64,
  Decimal and NSDecimalNumber.

- Improve serializeInteger performance to avoid overall speed regression.

e78l/swift-corelibs-foundation,parkera/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,parkera/swift-corelibs-foundation,parkera/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,e78l/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,parkera/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,e78l/swift-corelibs-foundation,e78l/swift-corelibs-foundation,alblue/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,apple/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,ikesyo/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,apple/swift-corelibs-foundation,apple/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,amosavian/swift-corelibs-foundation,parkera/swift-corelibs-foundation,apple/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,alblue/swift-corelibs-foundation,e78l/swift-corelibs-foundation,JGiola/swift-corelibs-foundation,bolshedvorsky/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,mattrajca/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,johnno1962b/swift-corelibs-foundation,alblue/swift-corelibs-foundation,alblue/swift-corelibs-foundation,amraboelela/swift-corelibs-foundation,johnno1962c/swift-corelibs-foundation