Stack Buffer Overflow in curl's OpenSSL Provider Handling

I found a stack buffer overflow in curl's OpenSSL provider handling code. The bug is in `ossl_set_provider()` function located in `lib/vtls/openssl.c`. When a provider name longer than `MAX_PROVIDER_LEN` is passed, the function copies it to a fixed-size buffer without proper length checking, …

memcpy(name, curlx_str(&prov), curlx_strlen(&prov));
name[curlx_strlen(&prov)] = 0;