Update fee estimator for topics with custom fees

### Background

HIP-991 introduced topics with custom fees. The creation fee for such a topic is higher than for regular topics. The fee estimator must be improved to include this option.

### Acceptance Criteria

1. The fee estimator calculates the fees for creating a topic with custom fees correctly.
2. The fees for regular topics are still estimated correctly.

### Dependencies

_No response_

### 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

No file or test is named in the issue. Start by locating the fee estimator and the implementation of HIP-991 custom topic fees, then run the existing fee-estimation tests. Done means custom-fee topic creation is estimated correctly without changing estimates for regular topics.

Written by the indexing model from the issue text.