Update to CMake installation of TriggerMenuRulebook

Addressing [ATR-30769] in a follow-up to (access-restricted MR) TrigMenuRulebook!775.

I found it simplest to source the setup script in the ART execution command, rather than try to propagate the environment out from setupTrigMenuRulebook.sh. Other than that, the changes are very minimal.

One thing that could be nice but was inconvenient to do for the moment, as we want a quick fix, is to split up the setup such that we can do:

1. Clone & install RB
2. Generate jsons (relatively slow athena job)
3. Run update_inputs.sh script to symlink the generated jsons
4. Execute runRulebook.py This would just speed up the failure in case something causes the RB clone & installation step to fail (e.g. local test with incorrect authentication). Less problematic for the automated testing, although in the same situation one might negligibly reduce test machine load.

FYI @martindl @gipezzul @shanisch @scella