[Sentry] Error: No metadata found for 'frequentRpcList'

### What is this about?

> [!IMPORTANT]
> See https://github.com/MetaMask/core/issues/5545

Sentry error event: [No metadata found for 'frequentRpcList'](https://metamask.sentry.io/issues/6621422532/events/f19641a5bdac4a38aaa5a92cf3a11de9/)

```
Error: No metadata found for 'frequentRpcList'
at construct([native code])
at ResultError(ses.cjs:7676:17)
at reduce(app/store/getPersistentState/getPersistentState.ts:44:19)
at reduce([native code])
at deriveStateFromMetadata(app/store/getPersistentState/getPersistentState.ts:38:60)
at e.getPersistentState(app/store/getPersistentState/getPersistentState.ts:22:10)
at persistTransform(app/store/persistConfig.ts:102:30)
at reduce([native code])
at processNextKey(node_modules/redux-persist/lib/createPersistoid.js:71:31)
at id(node_modules/react-native/Libraries/Core/Timers/JSTimers.js:230:18)
at _callTimer(node_modules/react-native/Libraries/Core/Timers/JSTimers.js:111:7)
at JSTimers.callTimers(node_modules/react-native/Libraries/Core/Timers/JSTimers.js:359:7)
at .value(node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:428:27)
at fn(node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:113:12)
at .value(node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:368:9)
at .value(node_modules/react-native/Libraries/BatchedBridge/MessageQueue.js:112:10)
```

### Scenario

_No response_

### Design

_No response_

### Technical Details

_No response_

### Threat Modeling Framework

_No response_

### Acceptance Criteria

_No response_

### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

_No response_

Read app/store/getPersistentState/getPersistentState.ts and app/store/persistConfig.ts, starting at deriveStateFromMetadata and persistTransform. Trace how frequentRpcList is persisted and where its metadata is expected. Done means the missing-metadata error no longer occurs and relevant tests pass.

Written by the indexing model from the issue text.