`MustBeErased` marker

The marker was described in https://github.com/0xMiden/protocol/discussions/2899 together with other protocol changes. This issue mostly pulls out the relevant parts for the marker

### Summary
To support `FeeNote` we enhance the current mechanism of erasable notes. Specifically, we add an optional `MustBeErased` marker on output notes, which serves two purposes:
- its presence changes the fee computation (not inserted into the note tree, no long-term onchain storage)
- transactions which include non-erased notes with the marker are rejected in the batch kernel*
This marker, combined with a simple analysis of batch builder incentives guarantees erasure of the `FeeNote` at the batch level.

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*I wonder if we can skip this check in the batch kernel, because the batch-builder incentives would already soft-enforce this. Specifically, if the builder includes the tx with, but fails to erase, the MustBeErased-note, then they will end up paying out-of-pocket for the difference between the tx-kernel-computed lower expected_output_notes and whatever the batch kernel actually computes, which is total_output_notes.

So first of all, the batch builder will want to collect the fee from FeeNote, but if for some reason they decide not to, they will actually be penalized for it.