[feature](brpc) Support custom TLS verify callbacks

[Yukang-Lian]

What problem does this PR solve?

Issue Number: N/A

Related PR: selectdb/selectdb-core#7183

BRPC 1.4.0 does not pass caller-owned data to custom TLS certificate verification callbacks, and its verify setup can leave the callback wiring incomplete. This prevents Doris clients from applying protocol-specific certificate admission checks while retaining the peer certificate chain verification configured by BRPC.

This PR adds the two downstream BRPC patches used by SelectDB: callback userdata propagation and the verify-mode setup fix. It intentionally stays separate from certificate hot reload so each third-party change can be reviewed independently.

Release note

Add BRPC support for TLS verification callbacks with caller userdata.

Check List (For Author)

• Test: Applied the complete current Doris BRPC patch stack to the BRPC 1.4.0 source tree.
• Test: Built both brpc-static and brpc-shared successfully.
• Behavior changed: Yes. Custom verification callbacks can receive caller-provided context.
• Does this need documentation: No.

[hello-stephen]

Thank you for your contribution to Apache Doris.
Don't know what should be done next? See How to process your PR.

Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?