[DPE-4068] Convert all tests from unittest to pytest + enable/disable secrets in every test (#452)

* convert all tests to pytest

* remove secret remove hook

* Revert "remove secret remove hook"

Author: Lucas Gameiro

tests/unit/conftest.py

@@ -30,20 +30,3 @@ def juju_has_secrets(mocker: MockerFixture):
             JujuVersion, "has_secrets", new_callable=PropertyMock
         ).return_value = True
         return True
-
-
-@pytest.fixture
-def only_with_juju_secrets(juju_has_secrets):
-    """Pretty way to skip Juju 3 tests."""
-    if not juju_has_secrets:
-        pytest.skip("Secrets test only applies on Juju 3.x")
-
-
-@pytest.fixture
-def only_without_juju_secrets(juju_has_secrets):
-    """Pretty way to skip Juju 2-specific tests.
-
-    Typically: to save CI time, when the same check were executed in a Juju 3-specific way already
-    """
-    if juju_has_secrets:
-        pytest.skip("Skipping legacy secrets tests")