Add logs for plugins data

While loading data form plugin like tests,
config options etc we do not have enough logs
to debug if any plugins is missed.

It is difficult to debug in such cases where we do not
find config options registered by plugins,
For example: https://review.opendev.org/#/c/706785

Adding more logs to know what all data we are loading from
all plugins.

Change-Id: I09d2349a0e32c2265e6beb3dad4619ad33782a51

tempest/test_discover/plugins.py

@@ -194,11 +194,14 @@ class TempestTestPluginManager(object):
     def get_plugin_load_tests_tuple(self):
         load_tests_dict = {}
         for plug in self.ext_plugins:
+            LOG.info('Loading tests from Tempest plugin: %s', plug.name)
             load_tests_dict[plug.name] = plug.obj.load_tests()
         return load_tests_dict
 
     def register_plugin_opts(self, conf):
         for plug in self.ext_plugins:
+            LOG.info('Register additional config options from Tempest '
+                     'plugin: %s', plug.name)
             try:
                 plug.obj.register_opts(conf)
             except Exception:
@@ -209,6 +212,9 @@ class TempestTestPluginManager(object):
         plugin_options = []
         for plug in self.ext_plugins:
             opt_list = plug.obj.get_opt_lists()
+            LOG.info('List additional config options registered by '
+                     'Tempest plugin: %s', plug.name)
+
             if opt_list:
                 plugin_options.extend(opt_list)
         return plugin_options