Fix race conditions and improve robustness during socket I/O

[julianz-]

Fixed race conditions to make socket I/O more resilient during connection teardown.

1. BufferedWriter's write(): Added error handling to ignore common socket errors (e.g., ECONNRESET, EPIPE, ENOTCONN, EBADF) that occur when the underlying connection has been unexpectedly closed by the client or OS. This prevents a crash when attempting to write to a defunct socket.
2. BufferedWriters's close(): Made idempotent, allowing safe repeated calls without raising exceptions.
3. Needed to add explicit handling of WINDOWS environments as these are seen to throw Windows specific WSAENOTSOCK errors.

Includes new unit tests to cover the idempotency and graceful handling of already closed underlying buffers.

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This change is 

[codecov]

Codecov Report

❌ Patch coverage is 73.10924% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.16%. Comparing base (094088f) to head (2e35bcb).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #779      +/-   ##
==========================================
- Coverage   79.24%   79.16%   -0.08%     
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  Files          29       29              
  Lines        4201     4315     +114     
  Branches      538      550      +12     
==========================================
+ Hits         3329     3416      +87     
- Misses        728      755      +27     
  Partials      144      144              

[webknjaz]

Let's extract this into a separate PR.

[julianz-]

Not sure I understand. The only thing modified here was the docstring. This was to distinguish MockSocket which was already there from MockRawSocket which I am adding. Originally, I added the latter in the same file but had to move to test_errors.py because the linter said I had too many modules in test_makefile.py.