[fix](regression) Preserve external JDBC URLs in TLS mode

[Yukang-Lian]

What problem does this PR solve?

Issue Number: N/A

Related PR: #66289

Problem Summary: SuiteContext.connect() appended Doris mTLS parameters to every caller-provided JDBC URL and returned the rewritten string before opening a connection. External JDBC setup closures therefore did not run in TLS regression jobs. Keep connect() protocol-agnostic and open the exact URL supplied by the caller; the default Doris JDBC URL already receives its TLS options in Config.createDefaultDb().

Release note

None

Check List (For Author)

• Test: Unit Test: mvn -Dtest=SuiteContextConnectTest test (1 passed)
• Behavior changed: Yes. External JDBC connections now preserve their supplied URL and execute their setup closure when regression TLS mode is enabled.
• Does this need documentation: No

[hello-stephen]

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