0308 load cluster hocon to generate app.config

[zmstone]

Fixes EMQX-10893

Release version: v/e5.6.0

Summary

Prior to this change, cluster.hocon was not loaded to generate app.<time>.config,
because it might change after boot.
This behavior lead to an issue for logging behaviour since logger has to be configured before the node boot.

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|breaking)-<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

[thalesmg]

Q: should this take into account legacy cluster-override.conf files as well?

[zmstone]

Q: should this take into account legacy cluster-override.conf files as well?

no, it's been quite long since the deprecation
this only affects log configs all other configs are not intended in cluster*.{conf|hocon}

[zhongwencool]

It works!