feat: improve formatting implementations

[DaniPopes]

Improve formatting implementations by first writing to a local buffer, then using fmt::Formatter::pad_integral to apply padding and all the other flags.

• Closes string: Do we want to write 0 for BITS == 0. #232
• Closes Support integral padding in formatting directives for Uint #295
• Closes uint's don't zero-pad when formatted with formatting specifier #369

This also standardizes the way the numbers are formatted to the same format that the standard library uses.

• Closes Do not 0 pad on debug and hex formatting #346