Add -v flags to spk-convert-pip and update spk convert to pass verbosity through

[dcookspi]

This adds -v/--verbose option flag to the spk-convert-pip script to change the logging level. It updates spk convert ... command to pass the verbosity level through to the underlying spk-convert-... command, and adds debug logging to show the underlying command.

This allows -v to be used to turn on/up debugging messages for both the spk convert ... command and the underlying script with one option, or turn on debugging for just the underlying script.

For example:

# increase the verbosity for both
> spk convert pip -v -- somepackage --python-version 3.9 --python-abi cp39
> spk convert pip -vv -- somepackage --python-version 3.9 --python-abi cp39

# increase the verbosity for the underlying script only
> spk convert pip -- somepackage --python-version 3.9 --python-abi cp39 -v
> spk convert pip -- somepackage --python-version 3.9 --python-abi cp39 -vv