fix interpolate missing values setting on stacked areas

[alxnddr]

Closes #38682

Description

Fixes stacked areas with "Replace missing values with Linear interpolated" setting. Here is the visual explanation of how it works:

How to verify

Ensure stacked area chart with "Replace missing values with Linear interpolated":

• interpolates area polygons when all series have nulls
• replaces nulls with zeros if at least one series in the dataset has non-null value

Example query

select 1 x, 10 y1, 20 y2, 30 y3
union all select 2, 10, null, 30
union all select 3, null, null, 30
union all select 4, null, null, null
union all select 5, 10, null, 30

Demo

Before

After

DC.js

Checklist

• Tests have been added/updated to cover changes in this PR

[replay-io]

Status	Complete ↗︎
Commit	6cb027f
Results	❌ 177 Failed ⚠️ 1 Flaky ✅ 2039 Passed