[ETCM-939] refactor Ledger (by removing it)

[jvdp]

It's been a journey; it looks easy enough on the src/main side but lots of stuff in src/test unfortunately broke along the way. The commits mostly tell a story of getting more tests passing while moving stuff out of Ledger gradually.

[lukasz-golebiewski]

Looks good overall, aside from some commented out code that could be removed

[leo-bogastry]

A description of what you did with the stuff that was in the Ledger would be nice

[AnastasiiaL]

nice to see tests simplified 👍

[jvdp]

A description of what you did with the stuff that was in the Ledger would be nice

Basically it was a layer that didn't add much except for complexity. I looked at the dependents and made the following changes:

• passed Consensus directly wherever that attribute was used
• checkBlockStatus wasn't used at all (removed)
• getBlockByHash was only used in CheckpointingService, logic was moved there
• importBlock was moved to the BlockImport class (it was very tightly coupled to it anyway)
• resolveBranch delegated directly to BranchResolution so this was just inlined in the one place it was used

The types aliases and case classes were moved to a package object and their own files respectively.