Interpolation Opion is missing in Graph + Single Stat

__Steps to reproduce:__
List the minimal actions needed to reproduce the behavior.

1. Create diagram of type Graph. Under Options your can specify the interpolation type e.g. "Smooth"
2. Create diagram of type Graph + Single Stat. Under Options the interpolation drop-down is missing

__Expected behavior:__
Like for Graph here is a dropdown to specify the interpolation type.

__Actual behavior:__
There is no dropdown for interpolation type.

__Environment info:__

* System info: `Linux 5.10.11-v8+ aarch64`
* InfluxDB version: `Version 2.0.4 (4e7a59b)`
* Other relevant environment details: Docker container `influxdb:2.0.4

__Config:__
All default

Start by locating the Graph and Graph + Single Stat diagram option entry points, then compare how the Graph interpolation dropdown is exposed under Options. Confirm the expected choices, such as Smooth, and verify that Graph + Single Stat offers the same interpolation control.

Written by the indexing model from the issue text.