Improved WebHostBuilder/HostBuilder like Storyteller bootstrapping

[jeremydmiller]

More analysis necessary here.

Something like:

public static int MainAsync(string[] args)
{
     return new StorytellerHostBuilder()
         .Services() // this is new. Have ST depend on having an IServiceProvider for the system,
                            // but happily use an empty stand in if it's not necessary
         .BeforeAll(Func<Task>) // probably lots of overloads here
         .BeforeEach(Func<ISpecContext, Task>) // and lots of overloads
         .AfterAll(Func<Task>)
         .AfterEach(Func<ISpecContext, Task>)
         .DisposeAfter(IDisposable)
         .ConfigureConversions(Action<Conversions>)
         .ConfigureLists(existing list options)
         .ConfigureEquivalenceChecks(Action)
         .WarmUp(Func<Task>) // Actions that need to be completed before any specs
                                                 // can be executed

         .Run(args) // This would be the only mandatory call
}

This should be everything you need to add more coarse grained extension methods like bootstrapping AspNetCore systems, starting/stopping Docker containers, running arbitrary command line calls, database setup/teardown, who knows what.