Add wall clock and CPU time measurements for raw read-outs, without decompression

[eguiraud]

...and clearly distinguish between "reading + decompression throughput" and "just raw reading throughput" in output.

[eguiraud]

Can use TBasket::LoadBasketBuffers after figuring out which seek position and number of bytes we want for a given entry range using TMath::BinarySearch(branch.GetWriteBasket() + 1, branch.GetBasketEntry(), entry);.