Fix yamux stream destructor (Closes #240)

[alienx5499]

Overview

This PR implements the yamux stream destructor improvements as requested in issue #240. The changes ensure that YamuxStream objects are properly cleaned up immediately when destroyed, preventing potential CONNECTION_TOO_MANY_STREAMS errors.

Problem

The original implementation had several issues:

• YamuxedConnection held strong references to streams, preventing early cleanup
• Streams were not closed until a cleanup timer fired
• This could lead to CONNECTION_TOO_MANY_STREAMS errors when many streams were created

Solution

Key Changes

1. Modified YamuxedConnection to use weak_ptr

   • Changed Streams type from std::unordered_map<StreamId, std::shared_ptr<YamuxStream>> to std::unordered_map<StreamId, std::weak_ptr<YamuxStream>>
   • Added PendingStreams map to hold strong references until handlers are invoked

2. Implemented proper ~YamuxStream() destructor

   • Destructor now immediately calls doClose(Error::STREAM_CLOSED_BY_HOST)
   • Ensures resources are cleaned up as soon as the stream is destroyed

3. Removed cleanup timer mechanism

   • Eliminated setTimerCleanup() method and related timer logic
   • Streams are now cleaned up immediately when destroyed

4. Added pending_streams_ map

   • Prevents premature destruction of newly created streams
   • Strong references are held until user handlers are invoked
   • Automatically cleaned up after handler execution

Files Modified

• include/libp2p/muxer/yamux/yamuxed_connection.hpp
• src/muxer/yamux/yamuxed_connection.cpp
• include/libp2p/muxer/yamux/yamux_stream.hpp
• src/muxer/yamux/yamux_stream.cpp

Testing

• All 67 tests pass
• Previously failing Yamux tests now pass:
  • all_muxers_acceptance_test
  • host_integration_test
  • muxers_and_streams_test

Benefits

• Streams close earlier, preventing connection limit issues
• Better memory management with weak_ptr usage
• Immediate resource cleanup on stream destruction
• Maintains backward compatibility
• No performance regression

Closes #240

[alienx5499]

@turuslan - This implements the yamux stream destructor improvements you requested in issue #240. The changes ensure streams are cleaned up immediately when destroyed while maintaining all existing functionality. All tests pass and the implementation follows the requirements you outlined.