Ensure durability during block import

[MegaRedHand]

We currently have multiple independent writes to the DB during block import. We should simplify this to have a single DB write to ensure durability

[dicethedev]

can you assign me this? @MegaRedHand

[MegaRedHand]

Sure. Since this issue isn't too detailed, I suggest you start by doing a high-level plan to ensure we're aligned