Reimplement input mirroring for OT milestone fields

[mikezzb]

Fixes #3173

• If the value in the text box for the OT/DT desktop milestone start/end field is changed, and the other android/webview milestone start fields are empty or were the same value as the desktop milestone previously, their values are also changed to match.
• If this value mirroring occurs, the touched property on these fields are all changed to "true" (which is how we know to update the field once the form is submitted).

Demo:

Screen.Recording.2024-03-22.at.01.13.40.mov