uv3 copy-on-write needs reset for moveToFirst/Last/fs

In v2, iterators may throw ConcurrentModificationException when an index is updated while it's being iterated over.

In v3, this is avoided by doing the minimal copy-on-write operation to the affected portion of the indexes.

There is an exception in v2 to this: 3 operations "reset" the modification tracking state to the current state of the index. These operations are those that move the interator to a known position. There are three API calls that do this: moveToFirst, moveToLast, and moveTo (meaning move to a position indicated by the passed-in FeatureStructure).

The corresponding operation for v3 has to be: for these three operations, if a copy-on-write operation has occurred, to reset the iterator to a fresh view of the current state of the underlying index (discarding the copy-on write version).