[Datagrid] "Split By" labels are not formatted correctly when splitting by date columns

[brianblakely]

Bug Report

Using repro: https://codesandbox.io/s/split-by-date-fmjmrf

If a "Split By" column is of date type, the label for the group in the datagrid is in epoch time.

Steps to Reproduce:

1. Add a date type column to the "Split By" field.
2. Ensure view is a datagrid.
3. Verify the group label.

Expected Result:

The date should be formatted as it is within a datagrid cell, such as M/D/YY.

Actual Result:

The date is displayed in milliseconds since epoch.

Environment:

Chrome 114.0.5735.198