Use consistent naming for initialisms in modagent module
Improve naming for initialisms (#468 (closed)) in modagent module. This MR does not include all changes but only the following:
- Rename rpcApiKeyType to rpcAPIKeyType in modagent module
- Rename WithJsonRequestBody to WithJSONRequestBody in modagent module
- Rename RpcApi type to RPCapi in modagent module
- Rename Api type to API in modagent module and found usages
- Rename invalidJson to invalidJSON in modagent module