Previously, we would update the `TxGraph` and `KeychainTxOutIndex`
first, then create a second update for `LocalChain`. This required
locking the receiving structures 3 times (instead of twice, which
is optimal).
This PR eliminates this requirement by making use of the new `query`
method of `CheckPoint`.
Examples are also updated to use the new API.
Upgrade:
- bitcoin to v0.31.0
- miniscript to v11.0.0
Note: The bitcoin upgrade includes improvements to the
`Transaction::weight()` function, it appears those guys did good, we
no longer need to add the 2 additional weight units "just in case".
