CLI: admin_only decorator

Addresses https://trac.openmicroscopy.org.uk/ome/ticket/5137

This PR should extend the `admin_only` decorator and implement it across all CLI plugins instead of using `try/except` blocks. Integration tests are also extended to test the admin check.
The only place where the decorator is not used is `fs sets --check` since the check is conditional to the argument being passed.

/cc @bpindelski 

----

--no-rebase