Make slice & clone do async seeks for DirectIO inputs #136046
Description
Description
related: #134803
It is common to slice and clone, but not actually read the bytes when using direct IO (consider all the places we construct FloatVectorValues but don't actually read any vectors...). Consequently, synchronously reading on every clone and seek, a file pos that we don't actually care about.
Maybe we can add a seekAsync that sets a couple of internal flags to indicate that the filepos isn't exactly correct and can be utilized in later seek and reads to indicate that things are prefetched.