fix(redis): RedisClusterBroker silently drops TLS config from BaseSecurity

[Lancetnik]

Description

RedisClusterBroker silently dropped TLS when configured with BaseSecurity(use_ssl=True): parse_security() conveys TLS via connection_class: SSLConnection, but CLUSTER_INCOMPATIBLE_PARAMS filters connection_class out in _resolve_url_options(), so RedisCluster(**opts) received zero SSL config and connected over plaintext (timing out against TLS-only clusters such as AWS MemoryDB). Introduced in #2854.

Fixes #2909

What changed

• RedisClusterBroker._resolve_url_options now translates TLS intent into RedisCluster's native ssl=True flag after the incompatible-params filter. This covers both BaseSecurity(use_ssl=True) and rediss:// URLs (which hit the same silent-drop path via parse_url's connection_class). setdefault is used so explicit user ssl/ssl_* kwargs are preserved, and the injected ssl option also flows into the sync Pub/Sub cluster client, which already reads it.
• Custom ssl_context on cluster: the async RedisCluster constructor has no ssl_context/connection_class parameter (verified against redis-py 7.4), so the fix proposed in the issue would raise TypeError at connect time. Instead a RuntimeWarning is emitted telling the user to use the ssl_ca_certs/ssl_certfile/ssl_keyfile/ssl_* options, while ssl=True is still applied — no more silent plaintext.
• _parse_base_security (plain RedisBroker): the generated SSLConnection._connection_arguments passed ssl: None when no explicit ssl_context was given, which disables TLS in asyncio.open_connection — the same bug in the non-cluster broker. It now falls back to ssl: True (default SSL context).

Verified end-to-end that the options produced by the broker construct a RedisCluster whose connection_kwargs["connection_class"] is redis-py's own SSLConnection, and that the issue's repro assertions are resolved.

Type of change

• Bug fix (a non-breaking change that resolves an issue)

Checklist

• My code adheres to the style guidelines of this project (just lint shows no errors)
• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• Both new and existing unit tests pass successfully on my local environment
• I have ensured that static analysis tests are passing by running just static-analysis
• I have included code examples to illustrate the modifications

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