[misc] Move shared components to shared directory (#4286)

Moved the following directories:

```
  - management/client → shared/management/client
  - management/domain → shared/management/domain
  - management/proto → shared/management/proto
  - signal/client → shared/signal/client
  - signal/proto → shared/signal/proto
  - relay/client → shared/relay/client
  - relay/auth → shared/relay/auth
```

and adjusted import paths

shared/management/client/rest/client_test.go

@@ -0,0 +1,34 @@
+//go:build integration
+// +build integration
+
+package rest_test
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/netbirdio/netbird/shared/management/client/rest"
+	"github.com/netbirdio/netbird/management/server/http/testing/testing_tools"
+)
+
+func withMockClient(callback func(*rest.Client, *http.ServeMux)) {
+	mux := &http.ServeMux{}
+	server := httptest.NewServer(mux)
+	defer server.Close()
+	c := rest.New(server.URL, "ABC")
+	callback(c, mux)
+}
+
+func ptr[T any, PT *T](x T) PT {
+	return &x
+}
+
+func withBlackBoxServer(t *testing.T, callback func(*rest.Client)) {
+	t.Helper()
+	handler, _, _ := testing_tools.BuildApiBlackBoxWithDBState(t, "../../server/testdata/store.sql", nil, false)
+	server := httptest.NewServer(handler)
+	defer server.Close()
+	c := rest.New(server.URL, "nbp_apTmlmUXHSC4PKmHwtIZNaGr8eqcVI2gMURp")
+	callback(c)
+}