[openssl/openssl] 162b5a: Fix a regression in X509_VERIFY_PARAM_add0_policy()

[Matt Caswell]

  Branch: refs/heads/openssl-3.1
  Home:   https://github.com/openssl/openssl
  Commit: 162b5a3483c16995a6f882a998e6a69ce44da016
      https://github.com/openssl/openssl/commit/162b5a3483c16995a6f882a998e6a69ce44da016
  Author: Matt Caswell <matt at openssl.org>
  Date:   2023-07-31 (Mon, 31 Jul 2023)

  Changed paths:
    M crypto/x509/x509_vpm.c

  Log Message:
  -----------
  Fix a regression in X509_VERIFY_PARAM_add0_policy()

Also fixes a similar regression in X509_VERIFY_PARAM_add0_table().

Commit 38ebfc3 introduced a regression in 3.0.6 that changed the return
value of the two functions above from 1 on success to the number of entries
in the stack. If there are more than one entry then this is a change in
behaviour which should not have been introduced into a stable release.

This reverts the behaviour back to what it was prior to the change. The code
is slightly different to the original code in that we also handle a possible
-1 return value from the stack push function. This should never happen in
reality because we never pass a NULL stack as a parameter - but for the sake
of robustness we handle it anyway.

Note that the changed behaviour exists in all versions of 3.1 (it never had
the original version). But 3.1 should be fully backwards compatible with 3.0
so we should change it there too.

Fixes #21570

Reviewed-by: Paul Dale <pauli at openssl.org>
Reviewed-by: Tom Cosgrove <tom.cosgrove at arm.com>
(Merged from https://github.com/openssl/openssl/pull/21576)

(cherry picked from commit e3d897d3fa3b48bb835fab0665a435469beea7ae)