Expose bump transaction and channel close events

[jjyr]

1. Repropose peer event broadcast Broadcast peer event #18 , now the channel broadcasts two new events: BumpChannelCloseTransaction and ChannelClosed
2. The Js caller receives new events without any change.
   1. BumpChannelCloseTransaction event hints wallet to broadcast channel close transaction through backend mempool in case the node failed to broadcast tx through P2P network.
   2. ChannelClosed event hint wallet a potential force closed event is occured.