chore: Add future deprecation note for component_(sent|received)_bytes_total metrics

[jszwedko]

Vector originally published two component bytes metrics:

• component_sent_bytes_total the number of serialized bytes successfully sent by sinks (before
  compression)
• component_received_bytes_total the number of serialized bytes successfully received by sources
  (after decompression and filtering)

These were intended to be used by users to understand the volume of data flowing in/out of sources
and sinks. However, they were dependent on the exact serialization format such that the same event
going into the socket source vs. vector source might be measured differently. To have
a consistent metric we then added:

• component_sent_event_bytes_total the number of "estimated JSON event" bytes successfully sent by a components
• component_received_event_bytes_total the number of "estimated JSON event" bytes successfully received by a components

This is a metric that is able to be compared between any two components. This removed a use-case of
component_(sent|received)_bytes_total. The remaining use-case users seemed to use this metric for
was as a proxy for network bytes, but what they really are interested in is the actual network
bytes. So we proposed two new metrics:

• component_sent_network_bytes_total the total number of bytes sent out on the network by a
  component
• component_received_network_bytes_total the total number of bytes received on the network by a
  component

Once those metrics exist, it isn't clear what use-case remains for
component_(sent|received)_bytes_total and so it would make sense to deprecate and remove them.

Signed-off-by: Jesse Szwedko [email protected]

[datadog-vectordotdev]

Datadog Report

Branch report: jszwedko/add-future-deprecation-note-for-component-bytes-metrics
Commit report: ffe2198
Test service: vector

✅ 0 Failed, 7 Passed, 0 Skipped, 25.45s Wall Time