feat: create namespace auto check if exist

[steinliber]

Signed-off-by: Meng JiaFeng jiafeng.meng@merico.dev

Pre-Checklist

Note: please complete ALL items in the following checklist.

• I have read through the CONTRIBUTING.md documentation.
• My code has the necessary comments and documentation (if needed).
• I have added relevant tests

Description

• plugin installed by helm support default namespace, with name pluginname
• update doc for override default value
• namepsace support upsert

Related Issues

close #1014

[daniel-hutao]

I think we can remove the create_namespace param and create ns when the ns is not exists.

[IronCore864]

I think we can remove the create_namespace param and create ns when the ns is not exists.

I agree with Daniel here; the param create_namespace seems redundant now.

[iyear]

LGTM