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/idp/v2/query.go

@@ -3,6 +3,7 @@ package idp
 import (
 	"context"
 
+	"connectrpc.com/connect"
 	"github.com/crewjam/saml"
 	"github.com/muhlemmer/gu"
 	"google.golang.org/protobuf/types/known/durationpb"
@@ -15,12 +16,12 @@ import (
 	idp_pb "github.com/zitadel/zitadel/pkg/grpc/idp/v2"
 )
 
-func (s *Server) GetIDPByID(ctx context.Context, req *idp_pb.GetIDPByIDRequest) (*idp_pb.GetIDPByIDResponse, error) {
-	idp, err := s.query.IDPTemplateByID(ctx, true, req.Id, false, s.checkPermission)
+func (s *Server) GetIDPByID(ctx context.Context, req *connect.Request[idp_pb.GetIDPByIDRequest]) (*connect.Response[idp_pb.GetIDPByIDResponse], error) {
+	idp, err := s.query.IDPTemplateByID(ctx, true, req.Msg.GetId(), false, s.checkPermission)
 	if err != nil {
 		return nil, err
 	}
-	return &idp_pb.GetIDPByIDResponse{Idp: idpToPb(idp)}, nil
+	return connect.NewResponse(&idp_pb.GetIDPByIDResponse{Idp: idpToPb(idp)}), nil
 }
 
 func idpToPb(idp *query.IDPTemplate) *idp_pb.IDP {