[lib] Stop using Ethers.js client from Wagmi

Summary:
In Wagmi 1.0 they switch from Ethers.js to their in-house alternative Viem.

Our ENSCache code is built on Ethers.js. I'll consider migrating that to Viem, but for now the easiest thing is to decouple it.

Depends on D9432

Test Plan:

1. Confirm that ENS resolution still works on mobile and web by opening up the inbox when I have recently chatted with an ENS user, and confirm that they ENS name is displayed
2. In combination with other diffs in the stack, I tested the following on both my local environment, and in a staging environment for my keyserver on comm.domains:
   • Mobile sign in with Rainbow wallet using Rainbow login
   • Mobile sign in with Rainbow wallet using WalletConnect login
   • Web sign in with Rainbow wallet using Rainbow login
   • Web sign in with Rainbow wallet using WalletConnect login
   • Web sign in with Metamask wallet

Reviewers: rohan, atul, ginsu

Reviewed By: atul

Subscribers: tomek, wyilio

Differential Revision: https://phab.comm.dev/D9433