Untangle / retangle opensslv.h, openssslconf.h and macros.h

Untangle / retangle opensslv.h, openssslconf.h and macros.h

When openssl/macros.h is included without openssl/opensslv.h, it can't
define OPENSSL_API_4 properly (with sufficient warnings enabled, the
compiler will complain about OPENSSL_VERSION_MAJOR not being defined).
The quick fix could have been to include openssl/opensslv.h in
openssl/macros.h, but that would create a nasty include loop, since
openssl/opensslv.h includes openssl/opensslconf.h, which includes
openssl/macros.h, in an order that leads back to macro check errors.

The objective is to make these headers more independent:

- openssl/opensslconf.h should really be completely independent, as it
  only defines macros for configuration values.  However, it needs to
  include openssl/macros.h for backward compatibility reasons.  We do
  this at the very end, under inclusion guards.
- openssl/macros.h is changed to include openssl/opensslconf.h, so it
  gets necessary configuration values to build some macros.  This will
  not cause an endless inclusion loop, since opensslconf.h's inclusion
  of macros.h is under guard.
- openssl/opensslv.h is changed to include openssl/macros.h instead of
  openssl/opensslconf.h.

Only one last piece needs to be done to make openssl/macros.h
independent from openssl/opensslv.h.  We can realise that the
definition of OPENSSL_API_4 doesn't need to depend on the current
version number.  There's nothing in our configuration that  would have
OPENSSL_API_4 defined to 1, and if the user sets OPENSSL_API_COMPAT or
OPENSSL_API_LEVEL to a high enough value, we consider that a
deliberate and knowledgable action on their part.

Fixes #7874
Fixes #9601

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/9626)