[Agg-Based] Fill missing values setting seems to not be applied

[dej611]

Describe the bug:

No matter what's the missing value setting chosen on the UI, the tool seems to only apply the Linear one.

Take this visualization with missing values to zero setting:

Same chart in Lens

[elasticmachine]

Pinging @elastic/kibana-visualizations (Team:Visualizations)

[nickofthyme]

The chart fitting requires the full data to be passed, including null buckets, in order to fill the null buckets given the fitting function.

In the case of the aggs_based chart, we are sending the request with min_doc_count set to 1, thus filtering all null/empty buckets given the time interval. We are not defining min_doc_count is the Lens request.

{
  "aggs": {
    "2": {
      "date_histogram": {
        "field": "timestamp",
        "calendar_interval": "1m",
        "time_zone": "America/Phoenix",
        "min_doc_count": 1
      }
    }
  },
...

If we add the min_doc_count: controls.MinDocCountParamEditor option here...

https://github.com/elastic/kibana/blob/9009cb8cf2f2719604232a4cdc75061bf94b89af/src/plugins/vis_default_editor/public/components/agg_params_map.ts#L16-L20

...I get the Show empty buckets option, which if I disable that switch (seems opposite based on the wording but whatever), then I get all the buckets in that date range and the fitting functions work as expected.

Note, this is not the case with the count aggregation as Elasticsearch will return 0 instead of null preventing the fitting of the values.