checkbox fires "change" event on programmatic updates

[mollykreis]

🐛 Bug Report

This was originally reported to FAST, but the issue was closed because FAST was deprecated.

Original issue: microsoft/fast#5750

💻 Repro or Code Sample

🤔 Expected Behavior

Setting a checkbox's checked state programmatically should not trigger a "change" event.

😯 Current Behavior

Setting a checkbox's checked state programmatically triggers a "change" event that has no way of being distinguished from a "change" event triggered by interaction with the checkbox.

💁 Possible Solution

🔦 Context

We've had to put workarounds into other places within nimble to temporarily ignore "change" events while programmatically setting the state of a checkbox.

🌍 Your Environment

• OS & Device: [e.g. MacOS, iOS, Windows, Linux] on [iPhone 7, PC]
• Browser [e.g. Microsoft Edge, Google Chrome, Apple Safari, Mozilla FireFox]
• Version [e.g. 1.8.0]