Support batch iteration over spaces with cursor

[akudiyar]

Cursor is an iterator that encapsulates a state which includes such parameters as the data window (currently iterated batch of data), next key in the window and mechanisms for loading the next portion of data from the server.

Cursor must have the following configurable options:

• size of the batch

Cursor must be supported for both single and cluster storage.

[akudiyar]

The merged implementation is good for crud API but needs rework for box API to move out from using the offsets in iteration.

[dkasimovskiy]

Need to implement Tarantool 2.11 cursors.