Use the query start block for ReplyChannelRange response messages

Use the query start block for ReplyChannelRange response messages

C-Lightning versions prior to 0.10 (incorrectly) enforce that the
reply_channel_range first_blocknum field is set to at least the
value they sent in their query_channel_range message. Sending a 0
results in them responding with an Error message, closing open
channels spuriously.

Further, C-Lightning versions prior to 0.10 require that the
reply_channel_range first_blocknum is either the same block implied
as the last block of the previous reply_channel_range or one
greater. This is not only a creative interpretation of the spec,
but a perfectly reasonable implementation might still receive an
Error message in the case of replies split by an empty block.

This code is extracted and modified from a previous version of
the original query_channel_range PR in commit
44ba52ccf10bb0362ed2964b66ec2ae51e388161. The original commit is by
`bmancini55 <bmancini@gmail.com>`.