gh-85393: Handle partial and blocking .write in TextIOWrapper

[cmaloney]

Also improves non-blocking support (gh-57531) and unbuffered support (gh-61606)

While behavior doesn't (generally) change it adds a lot of new warnings so I feel this is more of a feature (support non-blocking and unbuffered!) than a bugfix.

TODO before non-Draft

• Review what type each warning should be
• Validate if should warn on None (if so, fix CPython test cases)
• Implement a blocking I/O write test like the one for BufferedIO (test_nonblock_pipe_write_bigbuf)
• Add a partial write test

• Issue: io.TextIOWrapper ignores silently partial write if buffer is unbuffered #85393

[cmaloney]

I'm at the PyConUS sprints, would appreciate a high-level review / if the approach I took here looks like what you expect. In particular I tried to keep behavior around all the unexpected potential return values from buffer.write but also add DeprecationWarning/RuntimeWarning for many. I'm planning to work on expanding tests for this tomorrow (clone of BufferedIO blocking test, tests for underlying writers that return all the bad values, partial write tests, etc).

cc: @vstinner, @serhiy-storchaka (commented on the underlying issue, but also was quite a while ago. If there's better experts or someone more appropriate let me know)