Add network egress resource (#357)

This change adds a new import resource which enables exposing Netbird
resources as Kubernetes services. This remove the need to add sidecars
to every pod.

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

* **New Features**
* Added a new `NetworkEgress` custom resource (`netbird.io/v1alpha1`)
with CRD, schema validation, and status/conditions.
* Extended controller functionality to create egress services and
translate egress rules into import `EndpointSlice` resources; egress
pods now include a kube-egress-forwarder sidecar.
* **Bug Fixes**
* Added missing deep-copy and declarative apply support for the new
`NetworkEgress` API types.
* **Documentation**
* Updated README/API reference and added example manifests for
`NetworkEgress` (including IP/FQDN target usage).
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Signed-off-by: Philip Laine <philip.laine@gmail.com>

.golangci.yml

@@ -65,6 +65,8 @@ linters:
           alias: admissionv1
         - pkg: k8s.io/api/policy/v1
           alias: policyv1
+        - pkg: "k8s.io/api/discovery/v1"
+          alias: discoveryv1
         - pkg: k8s.io/client-go/applyconfigurations/meta/v1
           alias: metav1ac
         - pkg: k8s.io/client-go/applyconfigurations/core/v1
@@ -75,6 +77,8 @@ linters:
           alias: appsv1ac
         - pkg: k8s.io/client-go/applyconfigurations/policy/v1
           alias: policyv1ac
+        - pkg: k8s.io/client-go/applyconfigurations/discovery/v1
+          alias: discoveryv1ac
 
         - pkg: sigs.k8s.io/gateway-api/apis/v1
           alias: gwv1