[reactor-optional] Credentials as adapter 8x

[a-TODO-rov]

alternative of #3838

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Note

High Risk
Touches authentication, token renewal, connection handshake, sentinel/cluster address resolution, and removes reactive() accessors—any regression affects security-sensitive connect paths and backward-compatible APIs across a very large diff.

Overview
Reactor-free credentials and streaming re-auth. A new CredentialsProvider SPI resolves credentials via CompletionStage and publishes updates through subscribeToCredentials (with a Subscription handle). The driver’s auth path (RedisHandshake, ConnectionState, RedisAuthenticationHandler) uses this SPI; RedisCredentialsProvider is deprecated but kept via AsyncCredentialsProviderAdapter and default bridges from credentials() / resolveCredentials(). TokenBasedRedisCredentialsProvider (Entra ID) is rewritten on futures, listener lists, and an optional Executor instead of Reactor sinks/fluxes. RedisURI stores CredentialsProvider internally and exposes getCredentialsProviderAsync() for the non-reactive path.

Connect and routing without Reactor on the hot path. Socket address resolution and initial connect (AbstractRedisClient, ConnectionBuilder, RedisClient sentinel lookup, cluster node suppliers) switch from Mono<SocketAddress> to Supplier<CompletionStage<SocketAddress>>, including sentinel master discovery implemented with scheduled timeouts and async commands. Master/replica topology refresh and read routing drop Mono/Flux in favor of CompletableFuture chains, Pair instead of Reactor tuples, and helpers like Futures.withTimeout / unwrapExceptions; ResumeAfter is removed.

API cleanup for reactive command access. Eager reactive() fields and methods are removed from standalone, cluster, multi-DB, and pub/sub connections; cluster reactive code and dynamic command factories obtain APIs via connection.commands(RedisReactiveCommands.factory()) (and cluster equivalents). StatefulRedisConnection.commands(CommandsFactory) is now required on implementations. Reactive tracing uses getTraceContextAsync with a ContextView→Map adapter.

Docs: User guide streaming-credentials example matches the new provider contract (CompletionStage, subscribeToCredentials, typo fix for redisClient).

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[atakavci]

might need to move it back into RedisCredentialsProvider and extend from it for binary compatibility.

[atakavci]

i didnt go till the end with this PR yet. so please correct me if i got the wrong sense around the approach.
what i have in mind is, instead of using an adapter, to keep up with RedisCredentialsProvider with every public API we have, but use/redirect it to leverage the CredentialsProvider anywhere we are using it. The default implementations and internal usage of it will be replacing the behaviour and get rid of utilizing mono/reactor while if someone has already provided their rector-version implementation they have, it will not be ignored and kick-in as it was. this will be backwards compatible, not binary may be(not sure) but at least compile time.

[atakavci]

this simply means breaking binary compatibility. if there are other spots we already broke it, then lets never mind.