This data seems like a waste, both for the client and for the server. Maybe it'd be more productive to reduce this to a simple statsv call.

This also has the side-effect of improving client-side overhead by doing debouncing and combining of multiple events, which is rather likely since deprecated call sites usually aren't lonely. Whereas right now, if a user is in the sample group, they create EventLogging beacons for every single deprecated function call as it happens.

We should convert statsd.js to use sendBeacon before we do this.