Add CapnProto message size limit

Why it matters

To prevent processing excessively large CapnProto messages that could lead to resource exhaustion or performance degradation. This limit enhances stability and control over input data size when using the CapnProto format.

How to use it

Users can adjust the maximum allowed CapnProto message size by setting the format_capn_proto_max_message_size parameter to the desired byte limit.