Move to Zerion / Refactor logic & UI

[bejitono]

This PR replaces Umarshal with Zerion and refactors business logic & UI for transaction history.

It does so by:

• Removing Transaction Group models used for demo purposes and defining a new Transaction Activity model.
• Replacing Unmarshal Client with Zerion Client.
• Implements view mapping logic (show appropriate asset based on tx type, currency/date formatting, etc.)
• Updates views based on latest designs. Adds a basic detail screen to inspect the tx on Etherscan.

Motivations for switching to Zerion:

• It gives us more granular details about assets being swapped, price in fiat terms, nft assets, etc. Umarshal was too basic for our needs (only a description along with Eth value)
• Zerion has almost everything you’d want to arrive at feature parity with other wallets (for some tx's it even provides you with tx inputs, e.g. for ENS registrations). Since it provides most of what we need it will allow us to experiment with new features quickly until we have our own proper input decoding.
• It will be a good benchmark for our own tx categorization.

Notes: You need to apply to get a Zerion api key (https://help.zerion.io/en/articles/5351183-how-can-i-get-a-zerion-api-key). I applied for a key to be used in the test flight app. Use the demo api key for testing purposes: Demo.ukEVQp6L5vfgxcz4sBke7XvS873GMYHy