Custom tokens show 0 balance after import

[zixxtech]

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@milos-ethernal

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             Issue 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 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

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