Add support for Azure Container Apps "init containers"

The new database migrations sample uses a separate project to start the EF Core migration: https://github.com/dotnet/aspire-samples/tree/main/samples/DatabaseMigrations

This will start another Azure container app. It would be great to have support for "init containers" with Azure Container Apps. These would run in the same app initializing before:
https://learn.microsoft.com/en-us/azure/container-apps/containers#init-containers