Add nullifier epoch verification to transaction prologue

To support epoch-based nullifier scheme, we need to verify a mapping between nullifier and an epoch index as described in https://github.com/0xPolygonMiden/miden-vm/discussions/356#discussioncomment-3344538. This will require the following changes:

- Compute the nullifier commitment as a sequential hash of `(nullifier, script_root, epoch_index)` tuples (vs. current `(nullifier, script_root)`.
- In the prologue, compute epoch index for each nullifier. Epoch index can be computed based on the block number in which the note was create - but we still need to figure out the exact parameters.
- Verify that the computed epoch index is greater than or equal to the epoch index provided via the nullifier commitment.