curl: libcurl: Integer truncation in curl_easy_ssls_import() causes TLS sessions to never expire

Summary: curleasysslsimport deserializes a TLS session blob and stores it in the in-memory session cache. In Curlsslsessionunpack lib/vtls/vtlsspack.c:311, the validuntil field is read as uint64t and cast directly to curlofft int64t with no bounds check — so a crafted blob encoding validuntil =...