This now takes the generation type or 'all' as the first argument,
and then the generator or 'all' as the second argument. File extensions
are detemined automatically from the generation type.
Scripts that were previously run via:
poetry run python ./SCRIPT_NAME.py
and have been moved, can now be run as:
poetry run SCRIPT_NAME
Some top-level scripts remain, where they only generate test vectors and
do not contain any Zcash logic. These now use the `zcash_test_vectors`
package, and can't be run directly unless this package is made available
in `PYTHONPATH`.