Feature/etcm 655

[AnastasiiaL]

Description

Stable changes from checkpointing:

• delayed fetching of new blocks from peers after the checkpoint was received internally, to give it time to get propagated without starting reorganisations right away
• Extend checkpointing_getLatestBlock RPC call with the parentBlock hash to only return the descendants of the previous checkpoint, update response type to exclude the situation when the hash returned without bockNumber of vice versa
• Update the size of the block queue where fetcher keeps all known forks in case those forks become main chain
• Enable logging of dead letters

[ten15bit]

just some linter-like comments 👍