The telemetry ping generated by the default browser agent is currently using a completely custom schema, which makes the Firefox telemetry service essentially unable to interact with it at all (see bug 1632138 for some of the problems this is known to cause). We should rewrite it based on the common ping format instead.

While we're here, we should normalize the build_version to include buildid, etc.

Current plan is to migrate to Glean, which I believe obviates this issue.