* ci(circleci): test Redis behavior against local Redis and print short tracebacks
The redis_caching_unit_tests job ran three legacy files against the shared remote Redis. The DualCache and
batch-read logic that never needed a server now lives in tests/unit/caching/test_dual_cache.py with a mocked
RedisCache, and the behavior that does need one (the increment-with-floor Lua script, read-through, deletes,
batch reads) moved to tests/integration, which starts a local Redis. test_returned_settings only read
REDIS_PORT and is replaced by a unit test of Router.get_settings
CircleCI pytest runs now use --tb=short so failure output stays readable in the test results tab
* ci(integration): print short tracebacks from run.py and allow Redis in the sdk shard
