Make has_urls a decorator.

This ensures that the first URLs fetch call is only made when it has to
be made. No needless prefetching.
Drop the default loggers and add usual channel.

Use the same channel as for the rest of the logging. Keeps the output
homogeneous as simtools.uhttpclient depends largely on this logger.
Expose CLI and make cli_args an attribute of self.

Allows Test suites to add their own command line argument since CLI
parsing has now been deferred to object initialization and NOT module
load.
plan_id is a required CLI argument