[lineage] Use an auto-refreshing RESTMapper (#1497)

## What this PR does

Since the Cozystack extension API can now change dynamically while there
are live clients (the lineage webhook) querying this API, the REST
mapper of the client should "expect" that things may change and refresh
their discovery information when they get a cache miss to see if new
kinds have been registered.

### Release note

```release-note
[lineage] Use an auto-refreshing RESTMapper in the webhook's API client
that tries to update its API discovery info when it fails to GET a
resource kind that was previously not registered in its schema.
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- Refactor
- Streamlined webhook initialization by removing redundant
discovery/cache components, reducing startup complexity and overhead.
- Improved error handling during webhook setup for clearer diagnostics
on manager startup.
- Reduced runtime dependencies to improve reliability across diverse
cluster environments.
- Minor import and initialization cleanups to align with current
controller-runtime practices.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

internal/lineagecontrollerwebhook/webhook.go

@@ -10,12 +10,10 @@ import (
 	"github.com/cozystack/cozystack/pkg/lineage"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime/schema"
-	"k8s.io/client-go/discovery"
-	"k8s.io/client-go/discovery/cached/memory"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/rest"
-	"k8s.io/client-go/restmapper"
 	ctrl "sigs.k8s.io/controller-runtime"
+	"sigs.k8s.io/controller-runtime/pkg/client/apiutil"
 	"sigs.k8s.io/controller-runtime/pkg/log"
 	"sigs.k8s.io/controller-runtime/pkg/webhook/admission"
 
@@ -52,13 +50,15 @@ func (h *LineageControllerWebhook) SetupWithManagerAsWebhook(mgr ctrl.Manager) e
 		return err
 	}
 
-	discoClient, err := discovery.NewDiscoveryClientForConfig(cfg)
+	httpClient, err := rest.HTTPClientFor(cfg)
 	if err != nil {
 		return err
 	}
 
-	cachedDisco := memory.NewMemCacheClient(discoClient)
-	h.mapper = restmapper.NewDeferredDiscoveryRESTMapper(cachedDisco)
+	h.mapper, err = apiutil.NewDynamicRESTMapper(cfg, httpClient)
+	if err != nil {
+		return err
+	}
 
 	h.initConfig()
 	// Register HTTP path -> handler.