fix(gen_rpc): ensure client/server use same driver

[qzhuyan]

Fix: https://emqx.atlassian.net/browse/EMQX-11185

• ensure client/server use same driver
• Also bump to gen_rpc 3.2.1

Fixes

Summary

🤖 Generated by Copilot at dd5807b

Updated the gen_rpc dependency to version 3.2.1 and renamed the rpc.driver configuration key to rpc.protocol in emqx_conf_schema.erl. These changes were made to fix a bug in the RPC communication and to align with the latest gen_rpc library.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Added property-based tests for code which performs user input validation
• Changed lines covered in coverage report
• Change log has been added to changes/(ce|ee)/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• Created PR to emqx-docs if documentation update is required, or link to a follow-up jira ticket
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• If changed package build workflow, pass this action (manual trigger)
• Change log has been added to changes/ dir for user-facing artifacts update

The base branch was changed.