* Introduce a `Slot` type
Instead of having some type definition that only was used in half of the
code or directly using `u64`, this adds a new unit type wrapper `Slot`.
This makes it especially easy for the outside api to know what type is
expected/returned.
* Change epoch duratioC
* rename all instances of slot number to slot
* Make the constructor private
Co-authored-by: André Silva <andrerfosilva@gmail.com>
Bastian Köcher
b6294418f8