[FEATURE] introduce refreshing user defaults configs

[bowenliang123]

Code of Conduct

• I agree to follow this project's Code of Conduct

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• I have searched in the issues and found no similar issues.

Describe the feature

Introduce feature of refresh user defaults config (which starts with three continuous underscores "___") from config file via kyuubi-admin cli and refresh/user_defaults_conf Rest API.

1. add refreshUserDefaultsConf methond in KyuubiServer to read user defautls configs from property file and apply config changes to server's KyuubiConf
2. add refresh/user_defaults_conf api to AdminRestApi calling refreshUserDefaultsConf of KyuubiServer
3. add config type userDefaultsConf in kyuubi-admin cli

This feature will

• help to apply user defaults conf without restarting server or losing connections
• load latest config for engine launch, e.g. spark related config spark.*

It won't

• affect the components already started and using the clone of server conf
• affect configs for launched engine instance

Motivation

No response

Describe the solution

No response

Additional context

No response

Are you willing to submit PR?

• Yes. I can submit a PR independently to improve.
• Yes. I would be willing to submit a PR with guidance from the Kyuubi community to improve.
• No. I cannot submit a PR at this time.

[bowenliang123]

#4077
A followup PR for adding REST Api doc for POST /admin/refresh/user_defaults_conf.

cc @ulysses-you.