[Eva] Renames partitioned_dataflow into iterator, partitioning into *_index.

Makefile

headers/header_spec.txt

src/plugins/value/engine/compute_functions.ml

src/plugins/value/engine/iterator.ml

src/plugins/value/engine/iterator.mli

src/plugins/value/engine/partitioning_index.ml

src/plugins/value/engine/partitioning_index.mli

src/plugins/value/engine/trace_partitioning.ml