#1844 More open customization of Polly use

[RaynaldM]

In certain contexts, we need to be able to fully tune the way Polly is used for timeouts and circuit-breakers, but not only that. With this in mind, I'm proposing in this PR to open up the use of AddPolly by adding :

public static IOcelotBuilder AddPolly<T>(this IOcelotBuilder builder, Dictionary<Type, Func<Exception, Error>> errorMapping)
     where T : class, IPollyQoSProvider<HttpResponseMessage> =>
     AddPolly<T>(builder, GetDelegatingHandler, errorMapping);

 public static IOcelotBuilder AddPolly<T>(this IOcelotBuilder builder, QosDelegatingHandlerDelegate delegatingHandler)
     where T : class, IPollyQoSProvider<HttpResponseMessage> =>
     AddPolly<T>(builder, delegatingHandler, ErrorMapping);

 public static IOcelotBuilder AddPolly<T>(this IOcelotBuilder builder)
     where T : class, IPollyQoSProvider<HttpResponseMessage> =>
     AddPolly<T>(builder, GetDelegatingHandler, ErrorMapping);

Thanks to this, we will be able to use our own implementations of IPollyQoSProvider<HttpResponseMessage>, QosDelegatingHandlerDelegate and Dictionary<Type, Func<Exception, Error>>

[raman-m]

@RaynaldM Please merge by Squash and merge option only :exclamation: :exclamation: :exclamation:

[raman-m]

Congrats! :partying_face:

And we don't need this branch anymore...