Add SocketStream method docstrings

[mmaxjr]

Summary

• Add short docstrings for the concrete SocketStream stream methods.
• Link each method back to the matching trio.abc interface documentation.
• Add a documentation newsfragment for issue Some functions and properties in the documentation have no docstring #3221.

Fixes #3221.

Tests

• py -3.14 -m py_compile src\trio\_highlevel_socket.py
• Runtime docstring smoke check for SocketStream methods
• py -3.14 -m pytest src/trio/_tests/test_highlevel_open_tcp_stream.py -q
• git diff --check

[A5rocks]

Not necessary since these do not show up in the docs. Anyways please do not generate PR descriptions with an LLM in the future!