set_proposed_finalizers should not have side-effects if transaction fails

[arhag]

Currently, the proposed finalizer policy will take affect even if the transaction is aborted. Instead, if the transaction is aborted, the chain should act as if the finalizer policy was not proposed. This requires changes to state stored in Chainbase, which means changes to the snapshot structure as well. Since this is the first time it is changing since Leap 5, we require adding a new version of the chain state (captured in database_header_object).

Note: It appears that we have made changes to Chainbase in the past without updating the version in database_header_object. The last official version in that object was 2 which was introduced with the changes for EOSIO 2.0. Since then we have made other changes to Chainbase without bumping to version higher.

Regardless, we should start using it now. To correct for the mistake of not touching this over the past updates, we should do the following:

1. Retroactively pretend that version 2 includes not just the changes introduced in EOSIO 2.0 but also every other change to Chainbase since then up to and including Leap 5.0. The comments should be updated to reflect this.
2. We should update the current_version to a new version 3 that captures the changes we introduce in this Spring 1.0 release.
3. We should also bump the minimum_version to 3.

Since we are changing Chainbase anyway, it would be good opportunity to remove kv_database_config from the global_property_object (and from the snapshot) in this version 3 as well.