Add support for sketches into the metric datamodel

[prognant]

Use-cases

Accurately represent distribution, perform operation on those, send sketches to endpoint that support that kind of data for better accuracy and flexibility.

Proposal

Based on the current supported metric types two option can be envisioned:

1. Switch an existing type to be the facade for sketches (e.g. the Distribution type)
2. Add a new Sketch type and expose conversion between relevant type in VRL

Option #2 seems more reasonable: no compatibility issue, user can do what they want if conversion are consistently implemented between relevant types. The sketch format would likely be ddsketch.

References

The problem: Streaming quantiles
Datadog approach: ddsketch

[tobz]

+1 for option 2.

I think Distribution should stay as-is, and option 2 follows more closely to the OpenTelemetry metrics stuff IIRC, where sketch type/parameters can be encoded such that downstream systems have enough information to interact with the data natively, allowing better passthrough/avoids loss of accuracy.

[jszwedko]

Closing since we do have a model for sketches now.