Multiple outputs in single cell should tab instead of scroll

The current behavior for when a cell has more outputs than can be displayed is to attach a vertical scrollbar. This leads to poor UX. Rstudio has solved this issue by storing each output in a separate tab. This leads to significantly better UX.

The issue proposes replacing the vertical scrollbar for cells with many outputs with separate tabs, as in RStudio. No files, tests, or entry points are named, so first locate the current multi-output rendering and related UI tests. Done means multiple outputs are presented in separate tabs with improved usability.

Written by the indexing model from the issue text.