feat: add /rule_engine API endpoint

[sstrigler]

Fixes https://emqx.atlassian.net/browse/EMQX-8507

Summary

🤖 Generated by Copilot at 9c6290a

This pull request adds a new feature to the rule engine API, which allows users to get and update the rule engine configuration via the /rule_engine endpoint. It also enhances the rule engine configuration schema by adding a reference field and a helper function. The pull request updates the swagger documentation, the localization files, the changelog, and the test suite accordingly.

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
• 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
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• Schema changes are backward compatible

[kjellwinblad]

Looks good to me!

[coveralls]

Pull Request Test Coverage Report for Build 4668222089

• 18 of 18 (100.0%) changed or added relevant lines in 3 files are covered.
• 31 unchanged lines in 12 files lost coverage.
• Overall coverage increased (+0.02%) to 81.103%

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Files with Coverage Reduction	New Missed Lines	%
apps/emqx_bridge/src/emqx_bridge.erl	1	91.2%
apps/emqx_mqttsn/src/emqx_mqttsn_frame.erl	1	63.48%
apps/emqx/src/emqx_broker.erl	1	87.64%
apps/emqx/src/emqx_cm.erl	1	91.89%
apps/emqx/src/emqx_connection.erl	1	87.96%
apps/emqx/src/emqx_limiter/src/emqx_limiter_server.erl	1	89.08%
apps/emqx/src/emqx_session.erl	1	87.65%
apps/emqx_connector/src/emqx_connector_jwt_worker.erl	2	92.54%
apps/emqx/src/emqx_channel.erl	2	87.64%
apps/emqx/src/emqx_flapping.erl	3	80.85%

Totals
Change from base Build 4642703850:	0.02%
Covered Lines:	25129
Relevant Lines:	30984

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💛 - Coveralls