[Eva] Moves functions for partitioning from transfer_stmt into partition.

src/plugins/value/engine/compute_functions.ml

src/plugins/value/engine/partition.ml

src/plugins/value/engine/partition.mli

src/plugins/value/engine/partitioned_dataflow.ml

src/plugins/value/engine/partitioned_dataflow.mli

src/plugins/value/engine/state_partitioning.mli

src/plugins/value/engine/trace_partitioning.ml

src/plugins/value/engine/transfer_stmt.ml

src/plugins/value/engine/transfer_stmt.mli