[WIP] Add GitHub agentic workflow for daily scanning

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Add a GitHub agentic workflow that runs daily and can be manually triggered. It should scan the source tree under src and look at all projects.

Avoid:

• Exclude test projects (which are usually grouped under a tests subfolder).
• Inside projects, don't ever change lines that have a comment marker at the end of the line that indicates that the line shouldn't be changed. I.e. NO-INCREMENT.

Do:

1. If the project defines a PackageValidationBaselineVersion property and it doesn't point to the latest available version on nuget.org, update it.
2. If the project sets IsPackable=true, change the property back to false. This property is only flipped to true when a package is getting released and should immediately get switched back.
3. Update the VersionPrefix property in the project. Do so by incrementing the third digit (the patch version). I.e. X.X.Y
4. If the project specifies an AssemblyVersion property, update it. It might be specified multiple
   times with different conditions. Update all of them except for the ones with a marker as indicated above in the avoid section. Update those by incrementing the third digit. I.e. X.X.Y.X.

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