The existing cashtabCache is poorly tested and, based on observing debug logs in prod Cashtab, I believe it is broken
The shape of the existing cashtabCache, an object with tokenId for keys, is bad for its use case and also difficult to migrate and test. Since there are possibly bugs in the existing cache, do not migrate -- instead start with a new cache.
Since we are starting with a new one, do it the right way. Token cache should be a map storing genesisInfo by tokenId.
We can't store a map in localforage, so add helper functions to convert cashtabCache to and from JSON.
Update existing mocks for new shape.
Add new tests to confirm migration and expected behavior.