For numbers from 0 to 252, compactSize unsigned integers look like regular
unsigned integers. For other numbers up to 0xffffffffffffffff, a byte is
prefixed to the number to indicate its length—but otherwise the numbers
look like regular unsigned integers in little-endian order.
Description
returns the size including the bytes required to represent the size; https://btcinformation.org/en/developer-reference#compactsize-unsigned-integers