Cleanup/simplify mbed TLS related define from autoconf

Cleanup/simplify mbed TLS related define from autoconf

Instead of a custom logic using 0/1 to be defined when the functions
are present or not, use the standard check and adjust the source code
accordingly.

Also not compile mbed key helper with MBEDTLS_SSL_KEYING_MATERIAL_EXPORT

The helper methods are only used when we don't have
MBEDTLS_SSL_KEYING_MATERIAL_EXPORT and mbedtls_ssl_export_keying_material.

Remove AEAD check that tests for presence of mbedtls_cipher_write_tag
and mbedtls_cipher_check_tag. Having an mbed TLS version that does not
support that is highly unlikely. It might have been a good check in
PolarSSL's time but is not today anymore.

This also adds some missing support for mbed 2.x related defines to
cmake based build.

Change-Id: I0f325800ebeb20bd5ef3ff78e5c5fcf0f6f74efd
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Frank Lichtenheld <frank@lichtenheld.com>
Message-Id: <20250715122957.22311-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32145.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>