Refactor deployer sub-components to share pod watchers and pod selectors

Follow-up to https://github.com/GoogleContainerTools/skaffold/pull/6606

Some deployer sub-components (e.g. the `PortForwarder`) are not defined per deployer, but once per skaffold configuration. In a multi-module project, these would be instantiated once for every module causing duplicate behavior, so they were implemented as singletons to circumvent this. However, each instantiation only uses the pod selector from the calling deployer, so pod selectors (and thereby tracked resources) are ignored by the sub component. We should fix this by sharing the pod selectors across these components so they track the correct resources.