Discover IBackgroundProcess using IoC in non-AspNetCore

While the new AspNetCore implementation now got support for registering IBackgroundProcess as services and resolve them with support for DI, we still miss this in the non-AspNetCore implementation.

Is there any plans of doing this @odinserj or would you be interested in a pull request following the same pattern as AspNetCore?

https://github.com/HangfireIO/Hangfire/blob/master/src/Hangfire.AspNetCore/HangfireApplicationBuilderExtensions.cs#L68

Start with Hangfire.AspNetCore/HangfireApplicationBuilderExtensions.cs at the linked registration logic, then locate the corresponding non-AspNetCore startup path. Compare how IBackgroundProcess services are discovered and resolved, and confirm that the non-AspNetCore implementation supports the same dependency-injection behavior. Done means non-AspNetCore applications can register and resolve IBackgroundProcess implementations through IoC.

Written by the indexing model from the issue text.