Custom tokens show 0 balance after import #7888
Description
Bug description
In MetaMask wallet after the token is added the balance is shown as 0 even tho the ''Add token" pop-up shows correct amount.
After some debuging I noticed that problematic tokens have "aggregators": ["Dynamic"] set and they always get zero balance in AccoutntsApiBalanceFetcher.fetch because API didn't return any value for them.
I opened #7879 which fixes it by calling RPC callback but noticed that this may not be the best solution since the callback is called for 0 balance tokens where some of those could be returned 0 from API and some zero filled and that potentially the fetch should handle this differently so I open this issue to spark a discussion on this bug.
Steps to reproduce
Add any token to wallet which has "aggregators": ["Dynamic"] to wallet
Screenshots of this problem
