stream_muxer(yamux): add ReadWriteLock to YamuxStream to prevent concurrent read/write corruption

Introduce a read/write lock abstraction and integrate it into `YamuxStream` so that simultaneous
reads and writes do not interleave, eliminating potential data corruption and race conditions.

Major changes:
- Abstract `ReadWriteLock` into its own util module
- Integrate locking into YamuxStream for `write` operations
- Ensure tests pass for lock correctness
- Fix lint & type issues discovered during review

Closes #793

tests/conftest.py

@@ -1,6 +1,5 @@
 import pytest
 
-
 @pytest.fixture
 def security_protocol():
-    return None
+    return None