Investigate dropping Arcs for references

[TheBlueMatt]

We should see if we can take advantage of the borrow checker to drop a bunch of Arcs and hold references in a number of places, may require #80, though. Should also look into nice things like dropping the secp_ctx in Channels and holding a reference to the ChannelManager one, too.

[TheBlueMatt]

Oops. We've made great progress here, but there's still a bunch of required Arcs.

[valentinewallace]

maybe rename to Update ChannelManager's Logger from Arc to Deref? or close + new issue?

[TheBlueMatt]

I think we also need a few ChainWatchInterfaces to not be Arcs - at least in Router and SimpleManyChannelMonitor, PeerHandler's Routing and ChannelMessageHandlers should not be Arcs (though I presume that may happen via @arik-so's ongoing work) as well.

[valentinewallace]

I realized I'm still assigned to this. @TheBlueMatt are there still TODOs for this issue?

[TheBlueMatt]

Hmm, no, likely not. There was some previous discussion to maybe swap the Derefs for impl Trait for Deref<Target=Trait> instead, or maybe BorrowMTarget=Trait>, but that's separate.