feat: support bootstrap_file on authentication for build-in-database

[zhongwencool]

Fixes https://emqx.atlassian.net/browse/EMQX-12593

close #8714, #9148 This feature needs to be used before enabling built_in_database authn, so it makes sense to add configuration items to it.

Use the same template for initialization as for importing users:

Import data only on build-in-dabase create.

Support for JSON, CSV files.

authentication = [
  {
    backend = built_in_database
    mechanism = password_based
    password_hash_algorithm {name = sha256, salt_position = suffix}
    user_id_type = username

    # new items
    bootstrap_file = "/opt/init_user.json"
    bootstrap_type = hash | plain
  }
]

Release version: v/e5.7.2

Summary

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