[openssl/openssl] d55fc0: Add thread pool design document (phase 1)

[Hugo Landau]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: d55fc027b9af85b1054cdbc017046a9070935086
      https://github.com/openssl/openssl/commit/d55fc027b9af85b1054cdbc017046a9070935086
  Author: Hugo Landau <hlandau at openssl.org>
  Date:   2022-11-14 (Mon, 14 Nov 2022)

  Changed paths:
    A doc/designs/thread-api.md

  Log Message:
  -----------
  Add thread pool design document (phase 1)

Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Tomas Mraz <tomas at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19455)