Store parsed system-file data

When we successfully parse an uploaded file, we need to store the data in state. When a node is restarted, it should read the data stored this way (except in the Genesis case, when the data does not exist yet).

This change is required because the file content may be corrupted after an incomplete upload. Relying on the file content can cause an ISS if a single node has to be restarted.

This applies to:
- fee schedules
- exchange rates
- configuration
- api-permissions
- throttles

Start by tracing the parsing and node-restart paths for fee schedules, exchange rates, configuration, api-permissions, and throttles. The change is complete when successfully parsed data is stored in state and restarts read that stored data, while the Genesis case handles data that does not yet exist.

Written by the indexing model from the issue text.