Update Azure Foundry doc to use the existing and new model constants #5200
Description
Describe the issue or suggestion
In this article the model names should use the recently added AIFoundryModel constants.
In this PR a new section dedicated to Azure Foundry Local was added
Same changes for https://learn.microsoft.com/en-us/dotnet/aspire/github/github-models-integration based on dotnet/aspire#12107