### _Why are the changes needed?_
This is a followup of #4843
To support load kubernetes conf during runtime, so that we can support more kuberntes contexts without restarting the kyuubi server.
### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible
- [ ] Add screenshots for manual tests if appropriate
- [x] [Run test](https://kyuubi.readthedocs.io/en/master/contributing/code/testing.html#running-tests) locally before make a pull request
Closes#4996 from turboFei/refresh_kubernetes_conf.
Closes#4996
807fb92e4 [fwang12] comments
d42d25af7 [fwang12] from conf
809a7d3df [fwang12] refresh
22743f9e5 [fwang12] save
dedebbe71 [fwang12] api
d6f58cfc7 [fwang12] refresh kubernetes config
Authored-by: fwang12 <fwang12@ebay.com>
Signed-off-by: fwang12 <fwang12@ebay.com>
1dd9db7492