Simplify test infrastructure

[ehelms]

Why are you introducing these changes? (Problem description, related links)

Running tests required going through forge test, an Ansible playbook whose
only jobs were installing nmap on the VM, generating an ssh-config from the
inventory, and shelling out to pytest. This indirection made it harder to run
tests directly, required a VM-side package install before every test run, and
obscured what the test runner was actually doing.

What are the changes introduced in this pull request?

• Replace nmap --script ssl-enum-ciphers in candlepin_test.py with
  openssl s_client to verify TLS version support. openssl is already
  present on the VM as a Candlepin prerequisite, eliminating the only reason
  forge test needed to install a package on the VM before running tests.
• Move ssh-config generation from forge test into a session-scoped autouse
  pytest fixture (generate_ssh_config in tests/conftest.py). The fixture
  reads the static inventory (defaulting to inventories/local_vagrant,
  overridable via OBSAH_INVENTORY) and writes .tmp/ssh-config before any
  test runs, so pytest can be invoked directly without going through forge.
• Simplify development/playbooks/test/test.yaml to just run pytest now that
  the nmap install and ssh-config generation are handled elsewhere.
• Add make test and make test-unit targets as a direct interface to the
  test suite. make test runs the full integration suite; make test-unit
  runs only tests/unit/ with no VM required.
• Update CI to use make test instead of ./forge test.

How to test this pull request

Steps to reproduce:

• Run unit tests locally without a VM:

  make test-unit
  

  All tests in tests/unit/ should pass with no VM or deployed environment.

• Run the full integration suite against a deployed environment:

  make test
  

  Confirm tests/feature/katello/candlepin_test.py::test_tls passes without
  nmap installed on the VM.

• Confirm forge test still works (now a thin wrapper around pytest):

  ./forge test
  

Checklist

• Tests added/updated (if applicable)
• Documentation updated (if applicable)

[ehelms]

There are things in here I think we should do for sure, the open question is testing interface:

• forge for consistency with development actions
• make since it will stream the testing output real-time rather than dump it at the end
• pytest directly which has the benefits of direct interaction, but the downsides of having to "remember" the baseline set of options we run it with today: --durations=10 -vv