Use of EVP_PKEY_decrypt() should be more secure #17319
Description
This came up in #15283 (comment).
Looks like ERR_clear_error() is not really constant-time due to
static ossl_inline void err_clear(...) in crypto/err/err_local.h
calling OPENSSL_free(es->err_file[i]) and OPENSSL_free(es->err_func[i]), where es->err_file[i] and es->err_func[i] should be NULL if and only if no error queue entry is present at index i.