ssl_cipher_get_overhead(): Replace size_t with int and add the checks

Replace the type of "mac", "out", and "blk" with int to avoid implicit
conversion when it is assigned by EVP_MD_get_size(),
EVP_CIPHER_get_iv_length(), and EVP_CIPHER_get_block_size().
Moreover, add the checks to avoid integer overflow.

Fixes: 045bd047 ("Add DTLS_get_data_mtu() function")
Signed-off-by: Jiasheng Jiang <jiasheng@purdue.edu>

Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/23935)