[keyserver] Update keyserver ENSCache to source Alchemy key via getCommConfig
Summary:
Now that we're able to configure the Alchemy key via getCommConfig, we should use that to load the Alchemy key for the keyserver's ENSCache. This requires an await invocation, which necessitated a slight refactor.
Depends on D7357
Test Plan:
- Create a keyserver/secrets/alchemy.json file with valid config
- Make sure my local keyserver is able to do ENS resolution in notifs
Reviewers: atul, varun, jon
Reviewed By: atul
Subscribers: tomek
Differential Revision: https://phab.comm.dev/D7366