[Lens] Fitting filling options for missing buckets

[flash1293]

Provide settings for Lens to specify fitting/filling options for missing buckets. Elastic-charts offers a variety of settings for this.

Parent issue: #17717

Unclear:
Is this a series level setting or a chart level setting or a layer level setting? What will be in the first iteration? Everything elastic-chart exposes? A little less? All of it seems a little overwhelming

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[wylieconlon]

I think every layer and series should have the same fitting function. I tried out some examples to see if I could come up with a reason to use two different fitting functions, but couldn't come up with a good example.

The best reason I could think of is if you are showing two layers with different time intervals, but I'm not sure this is a great visualization.

Also, I found that when using the count metric we don't apply the fitting functions because of the shape of the data. The most reliable way to trigger fitting functions for me is to use metricbeat data on Max of process.cpu.total.pct, which is a metric that is not continuous.

I think the form should be at the chart level, and the only option that I don't think we should support is "Explicit" because it requires an extra input.

[flash1293]

I think every layer and series should have the same fitting function. I tried out some examples to see if I could come up with a reason to use two different fitting functions, but couldn't come up with a good example.

Makes a lot of sense, thanks!

the only option that I don't think we should support is "Explicit" because it requires an extra input.

Sounds good to me as well. Why are you concerned about the extra input? Complexity we should avoid if it's not totally necessary?

[flash1293]

Depends on #67384

[wylieconlon]

Yes, the main reason is that it's extra complexity, but also that I don't know the use case for it. In the parent issue there were several requests for "Zero" as the most common explicit number

[flash1293]

Should be disabled for bar charts. Keep the state around but don't use it if a bar chart is selected. XY chart only for now to leverage elastic-charts.