Harden RSA public encrypt

Harden RSA public encrypt

Check the that the indicated output buffer length is large enough.

Fix EVP_SealInit() to initialise the output buffer length to the RSA
modulus length, not the input KEK length.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28517)

(cherry picked from commit f34b1ad17ba37a76a96e53be3813d88bf2b329f2)