Package Deprecation Automation

Currently, marking a package as deprecated in a package manager requires asking a privileged package feed collaborator or administrator, typically the engineering manager or the EngSys team, to mark the package as deprecated.

For example, a NuGet package is deprecated by logging into nuget.org and manually marking the package as such.
Admin also provides the deprecation message at that point.
If admin is OOF, the deprecation process is delayed.
The NuGet package deprecation workflow is described in the [Deprecation workflow](https://docs.microsoft.com/nuget/nuget-org/deprecate-packages).

I would like to see the process automated as a follow on to the following feature request:
https://github.com/Azure/azure-sdk-tools/issues/3848

In that request, I asked for the process of updating the README to reflect deprecation to be automated and the message standardized. Once that task is complete, the next step is to automate the updating of package managers to reflect the updated status of a newly deprecated package.

In a nutshell, I want the package manager page for each deprecated package to be automatically marked as deprecated once the deprecation PR is merged, and have the package page updated with the deprecation message pulled from the package README.

As per [3848](https://github.com/Azure/azure-sdk-tools/issues/3848). the README will be updated with a standardized message with links to the replacement library and migration guide where applicable.

The deprecation message from the README should be displayed on the package manager page for a deprecated package. This way we have consistency between the README and the message customers see in the package manager.