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

[affo]

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Description

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

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

Flink's catalog factory already forwards client.security.* options to the Fluss client generically — no connector code change is expected. Add FlinkCatalogTlsITCase proving this works end-to-end against a TLS-enabled cluster.

Depends on: server pipeline integration (#3792).

Estimated diff size: ~120 lines.

(Note: Spark coverage is split out into its own ticket for symmetry, since neither connector depends on the other.)

Willingness to contribute

• I'm willing to submit a PR!