Add doc section:Enable using a Cookie Session Store from DI

[Rick-Anderson]

From aspnet/Security#1719

@HaoK

we should have an explicit section recommending this pattern of how to configure options instances with things from DI in this doc maybe? https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options

public class UseSomethingFromDI : IConfigureNamedOptions/IConfigureOptions<YourOptions> {
       public CookieConfig(ISomethingFromDI thing) => _thing = thing;
       public void Configure([string name,] YourOptions o) { o.Thing = thing; }
   }
   services.AddTransient<IConfigureOptions<YourOptions>, UseSomethingFromDI>();

[HaoK]

We can also demonstrate a new in 2.1 API ConfigureOptions here as well maybe:

services.ConfigureOptions<UseSomethingFromDI> instead of services.AddTransient<IConfigureOptions<YourOptions>, UseSomethingFromDI>();, this uses reflection to basically do the same thing and also lets UseSomethingFromDI configure multiple option types if desired.

[HaoK]

Maybe this should go into a separate bug, but another good 2.1 options feature to doc eventually is the new IOptionsBuilder and related overloads, see aspnet/Security#1718 (comment) its related to this general idea of being able to more easily configure options with things from DI

[Rick-Anderson]

IOptionsBuilder was documented here

Moved to #10392

[Rick-Anderson]

@guardrex isn't this a dup of #10392
If so, copy over what you need and close this.