[lib] Add getAddressForName to ENSCache

Summary:
This is the second step to this Linear task: ENG-2588

Depends on D6264

Test Plan:

ALCHEMY_API_KEY=alchemykeygoeshere yarn test utils/ens-cache.test.js

Reviewers: atul

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D6265