Client: Run client without configuration file; Fix #6410

[voetberg]

Changes:
* Change RuntimeError(Config Not Found) to ConfigNotFound Error, config_get correctly handles those and returns a default client config. The RuntimeError was being caught in different places and causing conflict.
* Added typing for baseclient, initialization broken into functions to avoid typing conflicts for optionals, including an error check for the missing config.
* Added test to run multiple client commands without configuration file in place, including func decorator for extended testing if that's desired.

[rdimaio]

I checked the type errors (https://github.com/rucio/rucio/actions/runs/8441860751/job/23121972309?pr=6520) - in my opinion, they can be ignored. Both errors existed before this change (verified on master branch) and they are due to not properly checking if a variable exists before accessing it. They can be fixed later on when type hints are added to those parts of the code.

[voetberg]

I checked the type errors (https://github.com/rucio/rucio/actions/runs/8441860751/job/23121972309?pr=6520) - in my opinion, they can be ignored. Both errors existed before this change (verified on master branch) and they are due to not properly checking if a variable exists before accessing it. They can be fixed later on when type hints are added to those parts of the code.

I'm of this opinion too, I was considering fixing them but figured it outside the scope of this PR. Annoying errors, but trying to trace a blame and ending up at this unrelated pr would be more annoying.

[rdimaio]

LGTM but I think it's best if someone with more experience on the repository has a look as well