This allows us to intercept getblock on a non 0 exit when the block was
not found. We fill this with something meaningull in future commits.

Signed-off-by: Peter Neuroth <[email protected]>

We move the `geblock` call into a separate function. This allows us to
call if from various places in the future.

Signed-off-by: Peter Neuroth <[email protected]>

We introduce the peers array that contains the known set of connected
peers for future reference in case that we couldn't find the block we
are looking for.

Signed-off-by: Peter Neuroth <[email protected]>

In the case that we have peers left in the peers array and that we could
not find the block yet, we ask the next peer for the desired block.

Signed-off-by: Peter Neuroth <[email protected]>

`getblockfrompeer` was introduced in v23.0.0, we want to skip this path
if the version of bitcoind used is below that.

Signed-off-by: Peter Neuroth <[email protected]>

Changelog-Changed: Plugins: bcli: Add a path that tries to fetch blocks
from a peer if we can not find them locally.

Signed-off-by: Peter Neuroth <[email protected]>

Using `getblockfrompeer` requires a version equal or above 23.0.0

Signed-off-by: Peter Neuroth <[email protected]>

It is simpler to just iterate through the peerlist backwards.

Signed-off-by: Peter Neuroth <[email protected]>