Fork handling #544
Description
In #531 I made a fix for fork handling:
If the latest relayed block is no longer on the main bitcoin chain, there was a problem with relaying new blocks, as fetching the block from esplora would fail. Unfortunately, we need to supply the whole block header (not just the hash) when changing the tip, so I had to fetch the block header from elsewhere. The easiest would be to just store the latest blockheader in the contract, but that would require redeployment which I didn't really want to do because of Fiamma. Plus, it would increase gas cost, although that's maybe not that big of deal.
In the linked PR I went with a goldsky approach. If we can't get that merged or don't want to run the goldsky instance then we need the mentioned change in the contract, plus a change in the relayer