* Load tracing filter only from config and simplify logic.
* Configure the state storage in the config, not an environment variable.
This also changes the config so that the path is always set rather than being
optional, because Zebra always needs a place to store its config.
* add zebrad acceptance tests
* add custom command test helpers that work with kill
* add and use info event for start and seed commands
* combine conflicting tests into one test case
Co-authored-by: Jane Lusby <jane@zfnd.org>