UDP telemetry ingest tracks sequence id

[m3047]

As of two months ago, RVR can ingest telemetry via JSON in UDP datagrams as well as directly via Dnstap. The intended source of data is ShoDoHFlo (see m3047/shodohflo#11) although you're welcome to source the data another way.

The ShoDoHFlo dnstap_agent emits a monotonic sequence identifier which the consuming dns_agent already tracks.

The intent of this update is to track the same identifier as the default behavior. This will be transparent if you're using the ShoDoHFlo telemetry as your telemetry source, but it could be a breaking change for other telemetry sources. Direct Dnstap consumption is unaffected by this change, although eventually it will be removed (and should be considered deprecated once this change is completed).

A configuration parameter TELEMETRY_ID will be implemented with the default value "id". You can set it to None to achieve the existing behavior.

[m3047]

Done.