There is a possible race condition when both the latest block hash and
height are needed. Combine these in one struct and place them behind a
single lock.
Instead of relying on the user to ensure the funding transaction is
correct (and panicing when it is confirmed), we should check it is
correct when it is generated. By taking the full funding transaciton
from the user on generation, we can also handle broadcasting for
them instead of doing so via an event.
`wait` doesn't capture enough of what's going on, but also Java
Java doesn't accpet methods just called `wait`, as it conflicts
with existing sync primitives on all Objects.
When ChannelMonitors are persisted, they need to store the most recent
block hash seen. However, for newly created channels the default block
hash is used. If persisted before a block is connected, the funding
output may be missed when syncing after a restart. Instead, initialize
ChannelManager with a "birthday" hash so it can be used later when
creating channels.
The `ChannelKeys` object really isn't about keys at all anymore,
its all about signing. At the same time, we rename the type aliases
used in traits from both `ChanKeySigner` and `Keys` to just
`Signer` (or, in contexts where Channel isnt clear, `ChanSigner`).
Other includes calling timer_chan_freshness_every_minute() and in the
future, possibly persisting channel graph data.
This struct is suitable for things that need to happen periodically and
can happen in the background.
