refactor(tests): reduce eslint-disable comments with proper typing

refactor(tests): reduce eslint-disable comments with proper typing

- Add MockOCPPRequestService and MockOCPPIncomingRequestService interfaces
- Export TestChargingStation type for typed mock service access
- Remove 14 eslint-disable comments from ChargingStationFactory.test.ts
- Remove 4 eslint-disable comments from ConfigurationKeyUtils.test.ts
- Use Partial<ChargingStationOcppConfiguration> for missing config tests

Remaining 43 inline eslint-disable comments are all legitimate:
- no-empty-function: Testing empty callbacks
- require-await: Mock async implementations
- no-explicit-any: Testing validators with invalid inputs