Enable automatic image rebuilding for Windows images on `main` branch

[lbussell]

The .NET Docker infrastructure for automatically rebuilding images in response to base image updates is not enabled for Windows images on the .NET Docker main branch. My understanding is that this is deliberate to allow us to control our release schedule more closely. However, this leaves the door open for human error. Furthermore, the Windows container release schedule has been very consistent over the past year (every patch Tuesday, only a few images delayed by a few hours one time). Therefore, it would make sense to enable the auto-rebuilding functionality for Windows containers as a failsafe.

[lbussell]

[Triage] We should pursue this given that it can be a safety net - we also shouldn't need any changes to the schedule as we should be manually queueing these as part of the release checklist anyways.