feat: exchange gRPC server implementation to connectRPC (#10145)

# Which Problems Are Solved

The current maintained gRPC server in combination with a REST (grpc)
gateway is getting harder and harder to maintain. Additionally, there
have been and still are issues with supporting / displaying `oneOf`s
correctly.
We therefore decided to exchange the server implementation to
connectRPC, which apart from supporting connect as protocol, also also
"standard" gRCP clients as well as HTTP/1.1 / rest like clients, e.g.
curl directly call the server without any additional gateway.

# How the Problems Are Solved

- All v2 services are moved to connectRPC implementation. (v1 services
are still served as pure grpc servers)
- All gRPC server interceptors were migrated / copied to a corresponding
connectRPC interceptor.
- API.ListGrpcServices and API. ListGrpcMethods were changed to include
the connect services and endpoints.
- gRPC server reflection was changed to a `StaticReflector` using the
`ListGrpcServices` list.
- The `grpc.Server` interfaces was split into different combinations to
be able to handle the different cases (grpc server and prefixed gateway,
connect server with grpc gateway, connect server only, ...)
- Docs of services serving connectRPC only with no additional gateway
(instance, webkey, project, app, org v2 beta) are changed to expose that
- since the plugin is not yet available on buf, we download it using
`postinstall` hook of the docs

# Additional Changes

- WebKey service is added as v2 service (in addition to the current
v2beta)

# Additional Context

closes #9483

---------

Co-authored-by: Elio Bischof <elio@zitadel.com>

internal/api/grpc/org/v2/org_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 	"time"
 
+	"connectrpc.com/connect"
 	"github.com/muhlemmer/gu"
 	"github.com/stretchr/testify/assert"
 	"google.golang.org/protobuf/types/known/timestamppb"
@@ -138,7 +139,7 @@ func Test_createdOrganizationToPb(t *testing.T) {
 	tests := []struct {
 		name    string
 		args    args
-		want    *org.AddOrganizationResponse
+		want    *connect.Response[org.AddOrganizationResponse]
 		wantErr error
 	}{
 		{
@@ -159,7 +160,7 @@ func Test_createdOrganizationToPb(t *testing.T) {
 					},
 				},
 			},
-			want: &org.AddOrganizationResponse{
+			want: connect.NewResponse(&org.AddOrganizationResponse{
 				Details: &object.Details{
 					Sequence:      1,
 					ChangeDate:    timestamppb.New(now),
@@ -173,7 +174,7 @@ func Test_createdOrganizationToPb(t *testing.T) {
 						PhoneCode: gu.Ptr("phoneCode"),
 					},
 				},
-			},
+			}),
 		},
 	}
 	for _, tt := range tests {