feat: add all missing health checks for core kinds

[doxsch]

Description of your changes

This PR adds missing health checks for all remaining standard Kubernetes core resource kinds, bringing the Core API section fully implemented.

Kind	GVK	Pattern	File
Node	core/v1	Status-based (Ready condition True)	node.go
PersistentVolume	core/v1	Status-based (Bound or Available)	persistentvolume.go
ReplicationController	core/v1	Status-based (all replicas match)	replicationcontroller.go
Endpoints	core/v1	Always ready	endpoints.go
ResourceQuota	core/v1	Always ready	resourcequota.go
LimitRange	core/v1	Always ready	limitrange.go
Event	core/v1	Always ready	event.go

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit tests for my change.

[doxsch]

Hi @negz @sergenyalcin @turkenf @ulucinar could someone please take a look at this PR?

We are also waiting on a review for #167. Would be great if someone could check that one as well when they have a chance.

Is there an estimated release timeline for merging these?

Thank you.