We need to port what was implemented in PRs [1] and [2] on the ci-fmw's tobiko role to the test-operator.

Requirements:

1. there should be a default tobiko.conf with the values from [1](see cifmw_tobiko_tobikoconf_default)
2. that configuration could be overriden (see cifmw_tobiko_tobikoconf)
3. cifmw (test-operator role) will check whether ssh private keys for tobiko already exist (tobiko could have been executed before) on some common artifacts directory:
   1. if they already existed, they should be reused, i.e. the existing ones will be copied to the tobiko pod
   2. if they didn't exist, they should be created, saved on some common artifacts directory and copied to the tobiko pod

How to verify this ticket:

• run some tobiko scenario tests using the test operator. For example (tobiko will create some OSP workloads):

tox -e neutron -- tobiko/tests/scenario/neutron/test_port.py::PortTest

• run again the same tests, setting the env variable TOBIKO_PREVENT_CREATE=True (tobiko will reuse the previously created workloads and it needs to have the same ssh private keys in order to connect to them).

 [1] https://github.com/openstack-k8s-operators/ci-framework/pull/1044
 [2] https://github.com/openstack-k8s-operators/ci-framework/pull/1067