AAP-57817 Add Redis connection retry using redis-py 7.0+ built-in (#16176)

* AAP-57817 Add Redis connection retry using redis-py 7.0+ built-in mechanism

* Refactor Redis client helpers to use settings and eliminate code duplication

* Create awx/main/utils/redis.py and move Redis client functions to avoid circular imports

* Fix subsystem_metrics to share Redis connection pool between
  client and pipeline

* Cache Redis clients in RelayConsumer and RelayWebsocketStatsManager to avoid creating new connection pools on every call

* Add cap and base config

* Add Redis retry logic with exponential backoff to handle connection failures during long-running operations

* Add REDIS_BACKOFF_CAP and REDIS_BACKOFF_BASE settings to allow
  adjustment of retry timing in worst-case scenarios without code changes

* Simplify Redis retry tests by removing unnecessary reload logic

awx/main/analytics/subsystem_metrics.py

@@ -14,6 +14,7 @@ from rest_framework.request import Request
 
 from awx.main.consumers import emit_channel_notification
 from awx.main.utils import is_testing
+from awx.main.utils.redis import get_redis_client
 
 root_key = settings.SUBSYSTEM_METRICS_REDIS_KEY_PREFIX
 logger = logging.getLogger('awx.main.analytics')
@@ -198,8 +199,8 @@ class Metrics(MetricsNamespace):
     def __init__(self, namespace, auto_pipe_execute=False, instance_name=None, metrics_have_changed=True, **kwargs):
         MetricsNamespace.__init__(self, namespace)
 
-        self.pipe = redis.Redis.from_url(settings.BROKER_URL).pipeline()
-        self.conn = redis.Redis.from_url(settings.BROKER_URL)
+        self.conn = get_redis_client()
+        self.pipe = self.conn.pipeline()
         self.last_pipe_execute = time.time()
         # track if metrics have been modified since last saved to redis
         # start with True so that we get an initial save to redis