fix: improve the suggest msg for update conf failed

[zhongwencool]

Fixes https://emqx.atlassian.net/browse/EMQX-10834

• For certificates and keys that cannot be "", the prompt is very misunderstood

Tips: There may be some conflicts in the new configuration under `merge` mode,
Please retry with the `replace` mode.

• mute the /configs/ API ununcessary log to console.

Summary

🤖 Generated by Copilot at b1221e8

This pull request refactors the config loading commands and API to use a map of options instead of an atom for the loading mode. This enables the user to control the output of the commands and suppresses the output for the API. It also improves the error handling and suggestion messages for the config loading commands.

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

[zmstone]

misunderstood -> misleading ?