Issue #21036: Fix typo in macro name

_PY_HASHTABLE_ENTRY_DATA => _Py_HASHTABLE_ENTRY_DATA
Issue #21043: Remove the recommendation for specific CA organizations

Closes #21043 by updating the documentation to remove specific CA
organizations and update the text to no longer need to tell you to
download root certificates, but instead use the OS certificates
avaialble through SSLContext.load_default_certs.
asyncio: Ensure call_soon(), call_later() and call_at() are invoked on current
loop in debug mode. Raise a RuntimeError if the event loop of the current
thread is different.  The check should help to debug thread-safetly issue.
Patch written by David Foster.