[Feature Request/Question] Controller watch namespaces based on labels (and event sources)

Description

Based on the documentation, the controller is able to dynamically adjust the watched namespaces based on explicit namespace names (often provided through a config map or similar). A convenient extension to this would be able to watch namespaces based on the labels/annotations for a given namespace. I would be helpful if this was built into the machinery of the controller itself, so it could be controlled by some high level configuration

Motivation

Sometimes the creation of new namespaces that need to interact (be watched by) with the operator are done through workflows outside of the purview of the "operator admin". Currently, in order to ensure coverage of all namespaces, either (1) both workflows need to interact and inform the operator deployment when namespaces are added, or (2) the operator simply needs to watch all namespaces. This is where a third option, of only coordinating the appropriate labels would be beneficial

(Somewhat) Related Projects

https://github.com/kubernetes-sigs/hierarchical-namespaces/blob/master/docs/user-guide/concepts.md

Workarounds considered

Use the Kubernetes client itself to query for namespaces upon controller start, periodically poll for changes. Similarly, try to use some form of an Informer to get the same information

首先定位 controller 现有的显式 namespace 配置和 event-source 处理逻辑，然后审查 issue 中提到的 Kubernetes client 和 informer 方案。明确 label 和 annotation 的选择、高级配置，以及创建匹配 namespace 时的行为；完成的标准是 controller 监视所选 namespace，而无需协调 workflow 或监视所有 namespace。