The SDK uses only the native int and float64 types internally for values
that are specified as being "number" in schema, so for SDK purposes only
a float64 level of precision is significant.
To avoid any weirdness introduced as we shim and un-shim numbers, we'll
reduce floating point numbers to float64 precision before comparing them
to try to mimic the result the SDK itself would've gotten from comparing
its own float64 versions of these values using the Go "==" operator.
This is a first pass of an "approximately equal" function that tries to
mimic the reduced precision caused by the field reader abstraction in
helper/schema so that we can distinguish between meaningful changes to
the proposed new state and incidental ones that just result from the loss
of precision in the SDK implementation.
Martin Atkins