[lib] Add Blob service utils

Summary:
As decided in ENG-3534, we will use the comm-blob-service:// URI prefix for BLob service hosted media. This diff adds some utilities that will be used later to deal with these URIs.

Also added the Blob service config to lib/facts directory, inspired by the lib/facts/feature-flags.js.

Test Plan: Did some console.log to ensure they're working. These functions will be used and better tested in further diffs

Reviewers: atul, marcin, ashoat

Reviewed By: ashoat

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7615