Only update `NodeStakingInfo` for whole hbar changes to `stake`

### Problem

We often include a `MapUpdateChange` in the block stream for a `NodeStakingInfo` that is actually identical because the staking account's balance changed---but not by a whole hbar.

### Solution

Avoid such updates.

### Alternatives

_No response_

Start by tracing the block stream's MapUpdateChange handling for NodeStakingInfo and how fractional balance changes affect stake. Confirm the existing behavior and identify the relevant test coverage; the work is done when updates are emitted only for whole-hbar stake changes and redundant updates are no longer produced.

Written by the indexing model from the issue text.