Historyc Bridge: Improve the mechanism to switch to fallback provider when EL node is out of sync

[ogenev]

Currently, in History Bridge, we are switching to a fallback provider if the request to the EL node fails.

However, there are cases where the requests don't fail but the EL node is out of sync and doesn't update the latest block number.
This prevents us from pushing the latest headers into the network.

To prevent such issues, we want to switch to a fallback provider if we are unable to follow the chain and if we keep getting the same latest block from the EL node.