[TASK-367] SASL/PLAIN AUTH

[fresh-borzoni]

Summary

closes #367 #374

Add SASL/PLAIN authentication support to the Rust client, matching the Java Fluss client behavior.

• Core: Authenticate request/response, exponential backoff with jitter (matching Java's ExponentialBackoff), retriable auth error handling
• Config: security_protocol, security_sasl_mechanism, security_sasl_username, security_sasl_password, connect_timeout_ms
• Bindings: C++ and Python bindings expose all new config fields
• Tests: SASL integration tests (valid creds, wrong password, unknown user) for Rust, C++ and Python
• Infra: Consolidated Rust IT from per-module clusters into a single shared LazyLock cluster with dual listeners, enabling concurrent test execution
• Docs: Updated configuration and error handling pages for all three languages

[fresh-borzoni]

@luoyuxia @leekeiabstraction PTAL 🙏

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[fresh-borzoni]

@luoyuxia fixed issue with cpp tests, caused by additional \ used by formatter.
Would you mind to run CI/CD pipeline again to check?

[leekeiabstraction]

TY for the PR for such an important feature! Left some comments.

[fresh-borzoni]

@leekeiabstraction Ty, addressed comments, PTAL 🙏

[fresh-borzoni]

@luoyuxia @leekeiabstraction Rebased and fixed conflicts. PTAL

[leekeiabstraction]

TY for the PR!

[fresh-borzoni]

rebased

[luoyuxia]

@fresh-borzoni Thanks. LGTM. Merging..

[luoyuxia]

@fresh-borzoni Seems ci fails after merge this pr. https://github.com/apache/fluss-rust/actions/runs/22520032930/job/65243381417

[fresh-borzoni]

@fresh-borzoni Seems ci fails after merge this pr. https://github.com/apache/fluss-rust/actions/runs/22520032930/job/65243381417

Looking into this
UPD
#392