feat(group): group service to create, update, and delete groups (#10455)

# Which Problems Are Solved

This PR adds API definition and backend implementation for GroupService
to manage user groups.

# How the Problems Are Solved
* API definition to create, update, retrieve, and delete groups is added
* Command-side implementation to create, update, and delete user groups
as part of the GroupV2 API is added

# Additional Changes
N/A

# Additional Context
- Related to #10089, #9702 (parent ticket)
- User contribution: https://github.com/zitadel/zitadel/pull/9428/files
- Additional functionalities to list/search user groups, add
permissions, manage users in groups, group scopes will be added in
subsequent PRs.
- Also needs documentation, which will be added once the entire feature
is available

---------

Co-authored-by: Livio Spring <[email protected]>

internal/api/grpc/group/v2/integration_test/server_test.go

@@ -0,0 +1,27 @@
+//go:build integration
+
+package group_test
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/zitadel/zitadel/internal/integration"
+)
+
+var (
+	CTX      context.Context
+	instance *integration.Instance
+)
+
+func TestMain(m *testing.M) {
+	os.Exit(func() int {
+		ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
+		defer cancel()
+		CTX = ctx
+		instance = integration.NewInstance(ctx)
+		return m.Run()
+	}())
+}