Improvements to `find_exclusion`

[samanthalwong]

For runwise bkg generation: exclusion region should come from config['sky_map]['on_exclusion_region'] to avoid leakage of bright sources as ring artifacts into their acceptances

For normal bkg generation: exclude runs with known bright sources (Crab, Mrks, etc.) from being included at all - Tobias has something similar in his scripts in DL3-Analysis

[steob92]

I’d be more inclined to correctly implement the custom exclusion region than add an additional parameter. At the moment there is an option to exclude runs taken on a predefined list of sources.

Additionally we get the exclusion for extended sources based on their morphology with an option to override the default exclusion.

[samanthalwong]

Ok sorry I think these are just misunderstandings on my part as to how to use the exclusion regions so I will close this issue and fix my implementation instead

[steob92]

@samanthalwong Can you check out:
https://github.com/VERITAS-Observatory/gammapy-tools/tree/on_exclusion

It should pick up on the default on_region specified in the "sky_map" section. Can you test this? If its all good with you I'll change this so that the parameter is in "background" selection and then defaults to "sky_map" if it isn't specified by the user.