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

requirements/requirements.in

@@ -56,7 +56,7 @@ pyyaml>=6.0.2  # require packing fix for cython 3 or higher
 pyzstd  # otel collector log file compression library
 receptorctl
 sqlparse>=0.4.4   # Required by django https://github.com/ansible/awx/security/dependabot/96
-redis[hiredis]
+redis[hiredis]>=7.0  # requires 7.0+ for retry functionality on connection errors
 requests
 slack-sdk
 twilio

requirements/requirements.txt

@@ -433,7 +433,7 @@ pyzstd==0.18.0
     # via -r /awx_devel/requirements/requirements.in
 receptorctl==1.6.0
     # via -r /awx_devel/requirements/requirements.in
-redis[hiredis]==6.4.0
+redis[hiredis]==7.0.1
     # via
     #   -r /awx_devel/requirements/requirements.in
     #   channels-redis