feat: Add identify-push raw format support and yamux logging improvements

- Add comprehensive integration tests for identify-push protocol
- Support both raw protobuf and varint message formats
- Improve yamux logging integration with LIBP2P_DEBUG
- Fix RawConnError handling to reduce log noise
- Add Ctrl+C handling to identify examples
- Enhance identify-push listener/dialer demo

Fixes: #784

libp2p/utils/__init__.py

@@ -9,6 +9,7 @@ from libp2p.utils.varint import (
     read_varint_prefixed_bytes,
     decode_varint_from_bytes,
     decode_varint_with_size,
+    read_length_prefixed_protobuf,
 )
 from libp2p.utils.version import (
     get_agent_version,
@@ -24,4 +25,5 @@ __all__ = [
     "read_varint_prefixed_bytes",
     "decode_varint_from_bytes",
     "decode_varint_with_size",
+    "read_length_prefixed_protobuf",
 ]