Migrate a generalized Moat implementation to Moat.jsm module

We need to add support to Tor Browser to access new Moat APIs (see: tpo/anti-censorship/bridgedb#40025 (closed)). To do so we would need refactor the tor-launcher Moat code a fair bit, so instead we should just migrate and async/await'ify the relevant code to a Moat.jsm module rather than potentially break the legacy tor-launcher.