Audit fingerprinting overrides (MozBug 1834274)

From #42054 (closed): FF120 1834274 Implement the remote setting client for fingerprinting protection overrides.

The long story short is that the bug adds a remote settings collection to exempt some domains from fingerprinting protection.

In addition to the remote settings, there's a pref that follows the same JSON format: privacy.fingerprintingProtection.granularOverrides.

Open questions:

• How does all of this interact with RFP?
• Is there any default config at the moment? We disabled remote settings fetching in various ways, but we need to check what a default conf looks like at the moment.
• Shall we disable any of these mechanisms at the moment? Which one? "Remote" settings (the local dump for us), the pref, or both?

One search key for finding where these mechanisms are in the code might be OverriddenFingerprinting.

/cc @tjr