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>

go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/go-logr/logr v1.4.3
 	github.com/go-openapi/testify/v2 v2.6.0
 	github.com/google/uuid v1.6.0
+	github.com/netbirdio/kube-egress-forwarder v0.0.2
 	github.com/netbirdio/netbird v0.72.4
 	github.com/onsi/ginkgo/v2 v2.32.0
 	github.com/onsi/gomega v1.42.1
@@ -79,7 +80,7 @@ require (
 	golang.org/x/crypto v0.53.0 // indirect
 	golang.org/x/net v0.56.0 // indirect
 	golang.org/x/oauth2 v0.36.0 // indirect
-	golang.org/x/sync v0.21.0 // indirect
+	golang.org/x/sync v0.22.0 // indirect
 	golang.org/x/sys v0.46.0 // indirect
 	golang.org/x/term v0.44.0 // indirect
 	golang.org/x/text v0.38.0 // indirect