ssl: Clean up type handling in export_user_keying_material()

ssl: Clean up type handling in export_user_keying_material()

For this we actually change the API of the
format_hex{,_ex} functions by changing int
to size_t for length parameters. While we
call this function with int paramters in
a lot of places (usually BLEN), this will
not produce warnings under
-Wno-sign-conversion. And we're sure those
values are positive since format_hex already
uses size_t internally.

Change-Id: Id7bacec23edc6dcd94465c308ea2144c7329a0c1
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1301
Message-Id: <20251030145231.2792-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg34036.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>