Investigate `DateTimeFormat.formatToParts` for fingerprintability issues
From #19048 (moved):
We should verify that timezone and/or locale not leaked to web content by new API.
https://bugzilla.mozilla.org/show_bug.cgi?id=1289340
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DateTimeFormat/formatToParts