[openssl/openssl] 9170cc: Optimize the implementation of ec_field_size()

[K1]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 9170cc0398222778065e098e396b8eb8cd0de1d3
      https://github.com/openssl/openssl/commit/9170cc0398222778065e098e396b8eb8cd0de1d3
  Author: K1 <dongbeiouba at gmail.com>
  Date:   2024-01-31 (Wed, 31 Jan 2024)

  Changed paths:
    M crypto/sm2/sm2_crypt.c

  Log Message:
  -----------
  Optimize the implementation of ec_field_size()

No need to create and copy BIGNUM p, a and b, just call
EC_GROUP_get0_field() instead.

Reviewed-by: Tomas Mraz <tomas at openssl.org>
Reviewed-by: Paul Yang <kaishen.yy at antfin.com>
(Merged from https://github.com/openssl/openssl/pull/23313)