The `longevity_user` is used in the `rhel_els` long run and `test_tally_openshift_payg`post_stage_deploy tests.

Since they are using the same org, tally syncs in the openshift_payg tests have the potential to effect the results of the long run test.

We need to update the test_tally_openshift tests so that they have their own user(s). 

The user fixture:

@pytest.fixture(scope="session")
def application(longevity_user_app):
    return longevity_user_app 

Usages:

https://gitlab.cee.redhat.com/insights-qe/iqe-rhsm-subscriptions-plugin/-/blob/master/iqe_rhsm_subscriptions/tests/longrun/test_verify_rhel_els_payg.py?ref_type=heads#L18

https://gitlab.cee.redhat.com/insights-qe/iqe-rhsm-subscriptions-plugin/-/blob/master/iqe_rhsm_subscriptions/tests/integration/swatch_tally/test_tally_openshift_payg.py?ref_type=heads#L23

Acceptance Criteria:

• test_tally_openshift_payg.py tests should use a different user
• Create new user or find another user
• Credentials stored in Vault