Avoid filter when the entire split is within the timestamp bounds

[fulmicoton]

If we search for [ta, tb) and the split meta informs us that the split's timestamp are within the [tA..tB] range, with [tA..tB] ⊆[ta, tb) there is no need to do any filtering.

This issue is not entirely straightforward, because the split meta are not passed in the leaf requests.

One possibility might be to get the meta from the fast field and make sure those metadata are added into the hotcache if it is not there yet.