feat: Wait for channel to become available

[holzeis]

Before that PR we where only depending on a timeout and a lightning balance. However, this led to several error messages as a lightning balance does not mean the channel is usable.

The PR introduces a sync of the channel state every 5 seconds representing the following 3 states:

1. Unavailable: No channel exists
2. Establishing: Channel exists but is not usable yet
3. Available: Channel exists and is usable

ebe4fb219a61b1802e673723916a77b8bad79ad4 fixes a regression after merging https://github.com/itchysats/10101/pull/483: we can not assume there is always a channel available. The taker was trying to reconnect constantly if no channel was available or if it was in creation. It's hard to distinguish between a good and a bad usable channel (as it might be in creation) - I am using the short_channel_id now to distinguish if the channel is actually in a bad state or everything is fine.

[bonomat]

I'm taking over this last bit :)

[bonomat]

@klochowicz / @luckysori / @da-kami : please have another look at my fixup: 477e8e2 (#496). I don't think the logic is needed:

• if there is no channel,
  • is_first_channel_usable=false, try to reconnect
• if there is a channel
  • is_first_channel_usable=true: we are connected, no need to reconnect
  • is_first_channel_usable=false: we are not conncted, reconnect

is_first_channel_usable uses is_usable: channel.is_live(), which checks if channel_state=ChannelState::PeerDisconnected. So no need to have another check

[bonomat]

Rebased and going ahead to merge this.

bors r+

[bors[bot]]

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