Clean up [identity-feature-enable] options for old releases

Project tags API and application credentials API are default features
since Queens and we can now assume these features are available when
identity v3 API is available. Becuase queens and older releases are no
longer supported by tempest, we can drop the options to enable tests
for these features.

Also, access rules for application credentials has been a default
feature since train so we can also assume this feature is available,
because train and older releases are no longer supported.

Change-Id: I138ac02f61c5a0a22ce0d5ad2d600a09166a4764
diff --git a/releasenotes/notes/identity-feature-opt-cleanup-caracal-7afd283855a07025.yaml b/releasenotes/notes/identity-feature-opt-cleanup-caracal-7afd283855a07025.yaml
new file mode 100644
index 0000000..67f6ede
--- /dev/null
+++ b/releasenotes/notes/identity-feature-opt-cleanup-caracal-7afd283855a07025.yaml
@@ -0,0 +1,21 @@
+---
+upgrade:
+  - |
+    The following deprecated options in the ``[identity-feature-enabled]``
+    section have been removed. Project tags API and application credentials
+    API are now always tested if identity v3 API is available.
+
+    - ``project_tag``
+    - ``application_credentials``
+
+  - |
+    Default value of the ``[identity-feature-enabled] access_rule`` option has
+    been changed from ``False`` to ``True`` and now the access rule API is
+    always tested when identity API is available.
+
+deprecations:
+  - |
+    The Keystone access_rule is enabled by default since Train release and we
+    no longer need a separate config in Tempest to enable it. Therefore
+    the ``[identity-feature-enabled] access_rule`` option has been deprecated
+    and will be removed in a future release.