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/server/connect_middleware/translation_interceptor.go

@@ -0,0 +1,48 @@
+package connect_middleware
+
+import (
+	"context"
+
+	"connectrpc.com/connect"
+	"github.com/zitadel/logging"
+
+	"github.com/zitadel/zitadel/internal/api/authz"
+	"github.com/zitadel/zitadel/internal/i18n"
+	_ "github.com/zitadel/zitadel/internal/statik"
+	"github.com/zitadel/zitadel/internal/telemetry/tracing"
+)
+
+func TranslationHandler() connect.UnaryInterceptorFunc {
+
+	return func(handler connect.UnaryFunc) connect.UnaryFunc {
+		return func(ctx context.Context, req connect.AnyRequest) (connect.AnyResponse, error) {
+			resp, err := handler(ctx, req)
+			ctx, span := tracing.NewSpan(ctx)
+			defer func() { span.EndWithError(err) }()
+
+			if err != nil {
+				translator, translatorError := getTranslator(ctx)
+				if translatorError != nil {
+					return resp, err
+				}
+				return resp, translateError(ctx, err, translator)
+			}
+			if loc, ok := resp.Any().(localizers); ok {
+				translator, translatorError := getTranslator(ctx)
+				if translatorError != nil {
+					return resp, err
+				}
+				translateFields(ctx, loc, translator)
+			}
+			return resp, nil
+		}
+	}
+}
+
+func getTranslator(ctx context.Context) (*i18n.Translator, error) {
+	translator, err := i18n.NewZitadelTranslator(authz.GetInstance(ctx).DefaultLanguage())
+	if err != nil {
+		logging.New().WithError(err).Error("could not load translator")
+	}
+	return translator, err
+}