Add GitHub action functionality to auto-bump versions and disable packages after publishing

After a package is pushed to nuget.org, a PR should be automatically created to turn the package building off (set IsPackable to false) and the relevant versions are bumped.

In [azure/azure-sdk-for-net](https://github.com/Azure/azure-sdk-for-net), there's a bot that can open these PRs automatically. Example: https://github.com/Azure/azure-sdk-for-net/commit/36e66f6bb46438afea51042415e4fd6746eb55d4

From a chat conversation with @ViktorHofer , this could be a rough idea:

> The GH action / AzDO pipeline would run scheduled and could do the following:
> - Scan if any of the checked-in projects' PackgeId+VersionPrefix tuple is older than what's available on nuget.org. If not, stop.
> - Update each project
> - Update the PackageValidationBaselineVersion version property with the new nuget.org version.
> - Set the IsPackable property to false
> - Update the VersionPrefix property lines by incrementing the third digit.
> - Update all the AssemblyVersion property lines (if they exists). Skip lines that end with a marker like