logging: reduce grpc logging noise (#3329)

* Normalize gRPC logs to print at warn level only
* Fix grpcLogger level enablement

---------

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

internal/logger/log.go

@@ -35,6 +35,11 @@ import (
 	"google.golang.org/grpc"
 )
 
+// GRPCLogger returns a logger at warn level for gRPC logging.
+func GRPCLogger(l *slog.Logger) *slog.Logger {
+	return slog.New(newLevelHandler(slog.LevelWarn, l.Handler())).WithGroup("gRPC")
+}
+
 // ReplaceGRPCLogger replaces grpc's internal logger with the given logger.
 func ReplaceGRPCLogger(l *slog.Logger) {
 	replaceGRPCLogger(l)