Execute app service tests against static app service plans

[APErebus]

We have flaky issues in Calamari tests due to capacity issues creating app service plans.

To avoid this, we now have 3 static app service plans that all the test app services are created against. Each test now creates it's own app service against the static plan.

The plans are in the calamari-testing-static-rg resource group, but the per-test resources are created in their own resource groups, which are torn-down at the end of the test (not test fixture)