Clarify input vs. output directories in the validator CLI arguments

[mmagician]

This might be for a separate discussion/PR, but I find the argument names a little misleading: it's not immediately clear whether these are input directories or output directories, for example:

• genesis_block_directory is an output location, but
• genesis_config_file is an input location (here, path, not a directory, but the same argument applies)

Originally posted by @mmagician in #1774 (comment)

[Mirko-von-Leipzig]

Thanks! I agree our naming could use some help. Partially, the problem is that bundled mode conflates a lot of the names so we are both overly precise and vague all at the same time.

Ideally we would also simplify where possible. For example, we should be able to have --config <filepath> --output-dir <dir> where we could even elide --output-dir entirely and use the working directory.