[TLS] Validate TLS config pass-through for the Spark connector

[affo]

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Description

Part of #3786 (FIP-29: (m)TLS Support).

Wave 2 — depends on: server pipeline integration (#3792).

Spark's catalog already forwards all catalog options to the Fluss client generically — no connector code change is expected. Add SparkCatalogTlsTest proving this works end-to-end against a TLS-enabled cluster.

Depends on: server pipeline integration (#3792).

Estimated diff size: ~95 lines.

(Companion to the Flink connector ticket, #3794 — neither depends on the other.)

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• I'm willing to submit a PR!