[WalletConnect] Send dapp's origin in the request

[katspaugh]

Currently the WalletConnect app sends its host as the origin string. This makes the tx-service display a nice icon and the app's name in the history, but it's not very useful. Basically all non-Safe App transactions are either WalletConnect, or from the safe mobile apps, or direct contract interactions.

It would be more useful to send the connected dapp's origin instead. Or in addition to the WC origin to keep the app usage analytics intact.

E.g. if you're connected to OpenSea, send opensea.io as the dapp origin. This will allow us to add domain-based security checks on the Safe wallet side.

[katspaugh]

@mmv08's feedback:

• It should be a separate new field to keep origin as it was for analytics' purposes
• To make a new field, we'd have to modify web-core, the SDK and the backend (tx-service should save it in the tx entity)

[katspaugh]

Since adding a completely new field is a lot of work across frontend, SDK and backend, and it's only needed for the WalletConnect app, perhaps adding the dapp's host as a query param to the existing origin field would be simpler and work just fine. In the frontend, we already cut off everything sans the domain part from the origin string when sending it to the backend.