[3.14] gh-134698: Hold a lock when the thread state is detached in `ssl` (GH-134724...

[3.14] gh-134698: Hold a lock when the thread state is detached in `ssl` (GH-134724) (GH-137107)

* [3.14] gh-134698: Hold a lock when the thread state is detached in `ssl` (GH-134724)

Lock when the thread state is detached.
(cherry picked from commit e047a35b23c1aa69ab8d5da56f36319cec4d36b8)

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>
* Only lock the SSL context, not the SSL socket.

This solves a deadlock when a socket is blocked while waiting on data,
which ended up causing a major regression in 3.13.6 (see gh-137583).

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Co-authored-by: Peter Bierma <zintensitydev@gmail.com>