fixes#851
This includes all of the associated methods, such as
AsUint64, AsUint64Atomic, AsUint64Ptr, CoerceToUint64, SetUint64
SetUint64Atomic, SwapUint64, SwapUint64Atomic, AddUint64,
AddUint64Atomic, CompamreAndSwapUint64, CompareUint64
Only significant change as a result was converting the histogram
aggregator's `count` state field into an int64 from a `metric.Number`.
Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>