Support migrations for the same DbContext in the same assembly for multiple providers

Currently if you have the same DbContext that needs multiple providers, you have to create a different assembly for each provider migrations (as stated [here](https://learn.microsoft.com/en-us/ef/core/managing-schemas/migrations/providers?tabs=dotnet-core-cli)), this not only slows down the development but it forces the project architecture in a certain way (you need an assembly with the DbContext to be referenced by the multiple migrations assembly that then are referenced by the main project).
I think it would be better if the tools understand that if you create a migration with a different provider, it has to be treated as a different one, all in the same assembly (in different folders of course)