Implement `checked_div_by_fee_rate_floor` and `checked_div_by_fee_rate_ceil` methods to compute the maximum and minimum transaction weights.
These methods provide precise weight calculations using both floor and ceiling divisions.
- Introduce `checked_div_by_fee_rate_floor` for floor-based weight division.
- Add `checked_div_by_fee_rate_ceil` for ceiling-based weight division.
- Update `ops::Div` implementation for `Amount` to use floor division by default.
- Include unit tests to validate both floor and ceiling division methods.
We have a bunch of functions and impl blocks scattered around the place
for calculating fee from fee rate and weight.
In an effort to make the code easier to read/understand and also easier
to audit introduce a private `fee` module and move all the code that is
related to this calculation into it.
This is in internal change only.
jrakibi
Tobin C. Harding