Use normalized format in Hedera.encodeSystemTransaction()

### Background

All transaction have to use the new normalized format. Once the consensus node can deal with transactions that use `body`, we can migrate the transaction created in `Hedera.encodeSystemTransaction()`.

### Acceptance Criteria

1. The generated transaction follows the new normalized format.

### Dependencies

1. Prerequisite: #17448

### Definition of Ready (DoR) Checklist

- [ ] Clear acceptance criteria
- [ ] Clear and detailed description
- [ ] Dependencies identified
- [ ] Links to documentation
- [ ] Should be completable in 2-3 Days
- [ ] Initial draft of Low-level design document
- [ ] At least high level test plan
- [ ] Groomed/Estimated

### Definition of Done (DoD) Checklist

- [ ] Acceptance Criteria complete
- [ ] No Codacy issues greater than minor (in new code)
- [ ] JavaDocs updated/created
- [ ] Code commented
- [ ] Unit tests created/updated
- [ ] 80% test code coverage (in new code)
- [ ] Happy Path and major negative cases in HAPI tests as applicable

Start by reviewing Hedera.encodeSystemTransaction() and the prerequisite issue #17448 to understand the normalized transaction format and migration boundary. Update the generated transaction to follow that format, then verify the acceptance criterion with the relevant unit and HAPI tests described in the checklist.

Written by the indexing model from the issue text.