Increment finalizer policy generation on each block that proposes a new finalizer policy; also log when finalizer policy changes

[arhag]

The finalizer policy generation should increment each time a new finalizer policy is proposed in a block as we progress along a branch of a chain. Note that a block can only increase the finalizer policy generation by at most 1.

Also add some additional logs:

The logs below are all added to the default logger. Unless otherwise specified, the logs should be at the info level.

Log after processing a block that contains a new proposed finalizer policy. Log what the new finalizer policy should be (not just the diff) including its generation number. Provide as context the block ID in which this finalizer policy was proposed. This should be logged at the debug level.

Log within the context of a block (provide block ID) that the active finalizer policy has advanced. Meaning that the active finalizer policy for its previous block had a lower generation number than the one for this block. It is sufficient to just log the generation number it started from and moved to. We should repeat the actual finalizer policy contents again as well.