Added TryAs in RegistrationBuilder - a version of As that doesn't throw

[jonah1nine]

Sometimes a concrete type could implement multiple interfaces and the instance of the concrete type needs to be registered against those interface.

Currently, we have the options below:

1. AsImplementedInterfaces()

builder.RegisterInstance(instance).AsImplementedInterfaces();

Straightforward and neat! However, I try to avoid using this as it hides away registrations of types. My IDE can't help me find where a certain type is registered.

2. Explicitly registering against the interfaces

builder.RegisterInstance<IInterfaceA, IInterfaceB, IInterfaceC>(instance);
// or
builder.RegisterInstance(instance)
    .As<IInterfaceA>()
    .As<IInterfaceB>()
    .As<IInterfaceC>();

Still relatively straightforward and neat! In addition, I can now easily see what the instance is registered against. My IDE can easily find these registrations.

---

Now, there are cases where it is not guaranteed that an instance implements a certain interface, but still needed to be registered if it is. Option 1 can handle this easily as it will only register against implemented interfaces. However, option 2 will fail and rightly throw an exception.

A way around this is to manually check the instance against the interfaces:

var registrationBuilder = builder.RegisterInstance(instance);

if (instance is IInterfaceA)
{
    registrationBuilder = registrationBuilder.As<IInterfaceA>();
}
if (instance is IInterfaceB)
{
    registrationBuilder = registrationBuilder.As<IInterfaceB>();
}
if (instance is IInterfaceC)
{
    registrationBuilder.As<IInterfaceC>();
}

This is cumbersome the more interfaces you need to check against.

---

This PR adds a new version of As that doesn't throw an exception if the instance does not implement the interface it's being registered against: TryAs

With this, we can write above similar to option 2:

builder.RegisterInstance(instance)
   .TryAs<IInterfaceA>()
   .TryAs<IInterfaceB>()
   .TryAs<IInterfaceC>();

Back to straightforward and neat!

Note: I went for a very simple implementation and just added a boolean flag to the AddInterfaceType method. Feel free to come up with a better implementation.

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