Move extension methods to Extensions folder

[hishamco]

This will help the developers to light up the extensions if the DI namespace is there, something like normal ASP.NET Core extensions for ServiceCollection and IApplicationBuilder. So, the user does not need to remember the namespace that holds the type

[github-actions]

This pull request has merge conflicts. Please resolve those before requesting a review.

[hishamco]

@gvkries I think this is helpful. Many times, we spend time because we don't know the original namespace

If it looks good, I will continue to finalize the PR

[gvkries]

I don't know, this is a massive change. Maybe break it up in smaller pieces, so it's easier to argue about.

I've only took a quick look, some of the changes seem to be good, others, well, controversial... E.g. IIRC you recently moved the IOrchardHelper extensions to the global namespace and here you're reverting that.
Additionally, I don't think that all extension methods should be in a extensions namespace, most of them make sense in the namespace of their target type. An example would be the BuildShapeContextExtensions.

[hishamco]

E.g. IIRC you recently moved the IOrchardHelper extensions to the global namespace and here you're reverting that.

Please let me know where, maybe it happen accidently

I don't think that all extension methods should be in a extensions namespace,

Of course not, mostly should be moved to Microsoft.Extensions.DependencyInjection