Migrate to Etherscan API as Alethio API is getting deprecated

[omnat]

Codefi team needs deprecate the Alethio API. This impacts MetaMask mobile users, so we should notify them of this disruption to avoid any confusion/panic.

User impact

With this deprecation, the received token transfers will stop working on mobile - so let's migrate to another service.
If we don't migrate, the incoming token transfers will be temporarily unavailable - users wouldn’t know of this and it cause them confusion unless we inform them sufficiently.

Task:

Utilize Etherscan API to show received tokens in the history. This will apply for tokens that have been added to the wallet, and for newly added tokens that match the token registry.

Note: We tested it locally that Alethio API deprecation would not cause unexpected issues on the mobile app. cc @estebanmino

[omnat]

Omna waiting to hear from Codefi team to put a date on the deprecation.

[omnat]

@omnat to ask for an Etherscan API key for this from Etherscan team

[omnat]

We have the API key, this is ready to be picked up. Shared with Esteban, but if someone else picks it up, please ping me for the key

[omnat]

Notes on Etherscan plan: https://roamresearch.com/#/app/MetaMask/page/x3jYpsW9a