[openssl/openssl] fe5c5c: evp_md_init_internal: Avoid reallocating algctx if...

[Tomas Mraz]

  Branch: refs/heads/master
  Home:   https://github.openssl.org/openssl/openssl
  Commit: fe5c5cb85197aec7d68ab095b866ed22076850d0
      https://github.openssl.org/openssl/openssl/commit/fe5c5cb85197aec7d68ab095b866ed22076850d0
  Author: Tomas Mraz <tomas at openssl.org>
  Date:   2022-05-02 (Mon, 02 May 2022)

  Changed paths:
    M crypto/evp/digest.c
    M crypto/evp/m_sigver.c
    M include/crypto/evp.h

  Log Message:
  -----------
  evp_md_init_internal: Avoid reallocating algctx if digest unchanged

Fixes #16947

Also refactor out algctx freeing into a separate function.

Reviewed-by: Dmitry Belyavskiy <beldmit at gmail.com>
Reviewed-by: Ben Kaduk <kaduk at mit.edu>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18105)