* Makes our existing mnemonic_generation.oy accessible as an interactive CLI utility for converting dice rolls or coin flips into 12- or 24-word mnemonics as well as the final word calculation.
* Reduces python dependencies in mnemonic_generation.py
* Removes need to always specify `wordlist_language_code`.
* Adds constants for number of dice rolls for each mnemonic phrase length (since 99 may become 100 soon).
* Generates test dice rolls, coin flips, or word selections via its "rand12" and "rand24" option.
* Adds support for coin flips, even though the SeedSigner UI does not support coin flips yet (and might not ever).
* Updates dice_verification.md accordingly.