Migration code

[ValarDragon]

IAVL fast node migration code

• We need to make a migrate function, that reads every 'live node' in the node db, and derives the corresponding fastNode if its a leaf, and sets it. This should be a standalone function which we can test.
• Then we should make an automatic way to test if the binary was upgraded. One way to do this is by making an entry in the nodedb at a specific key (perhaps with a v prefix), and the value at that key be a version number. If the version doesn't exist, or if its 1, then run this migration to get the new data.

[tac0turtle]

can this also be treated as upgrade and then the fast cache will populate on its own over time? Not all data will be added but the most touched parts?

[ValarDragon]

We can't do that and get fast iteration