Update plugin to use IPC endpoint instead of channel between application

[shuse2]

Description

• Update application to throw error if IPC is not enabled and plugin is registered
• Update plugin to use API client to connect to the RPC endpoint given by the config
• Remove events from the plugin

Acceptance Criteria

• All tests for the plugin should be passing

[shuse2]

Additional update required

1. Add missing endpoints
   • network_getStats (previously app_)
   • network_getConnectedPeers (previously app_)
   • network_getDisconnectedPeers (previously app_)
   • chain_getTransactionsByHeight (required if only broadcast header)
   • chain_getAssetsByHeight (required if only broadcast header)
   • system_getSchema (required to return block/transaction/asset schema for decoding)
2. Add/Update RPC event name
   • txpool_newTransaction (previously app_)
   • chain_newBlock (update to only broadcast header)
   • chain_deleteBlock (update to only broadcast header)
   • chain_forked (update to only broadcast header)
   • chain_validatorUpdate
   • network_newBlock (New event replacing app_networkEvent)
3. Consider adding engine start endpoint (no hook to run controller)
   • Add abi:ready
4. Update @liskhq/lisk-api-client to use metadata, schema and new endpoints
5. Update all RPC to return in JSON object to be consistent with module endpoints