ssl/statem: Replace size_t with int and add the checks

ssl/statem: Replace size_t with int and add the checks

Replace the type of variables with int to avoid implicit conversion when it is assigned by EVP_MD_get_size().
Moreover, add the checks to avoid integer overflow.

Fixes: 6594189 ("Merge early_data_info extension into early_data")
Fixes: 9368f86 ("Add TLSv1.3 client side external PSK support")
Fixes: 1053a6e ("Implement Server side of PSK extension parsing")
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/23937)