[DSI-8257] Simplify flow of cancellation tokens through .NET applications and interactions

[kruncher]

This came up whilst reviewing the PR for the recently introduced .NET profile component.

It is quite easy for developers to inadvertently omit passing cancellation tokens from application controllers to interactions when dispatching them via IInteractionDispatcher.

This PR introduces ICancellationContext which automatically manages the flow of cancellation tokens through the interaction framework.

In most cases developers can now dispatch requests without having to worry about manually passing cancellation tokens:

await interaction.DispatchAsync(
    new ExampleRequest {
        Value = 42,
    }
).To<ExampleResponse>();

or in the case of when mapped to a view model:

var response = await interaction
    .MapRequestFromViewModel<ExampleRequest>(this, viewModel)
    .To<ExampleResponse>();

Request's that should never be cancellable can be annotated with the [NonCancellable] attribute; for example,

[NonCancellable]
public sealed record WriteToAuditRequest
{
    ...
}

Developers are still able to explicitly override cancellation tokens if needed (unless [NonCancellable] is specified); for example,

await interaction.Build()
    .WithCancellation(CancellationToken.None)
    .DispatchAsync(new ExampleRequest {
        Value = 42,
    })
    .To<ExampleResponse>();

or in the case of when mapped to a view model:

var response = await interaction
    .MapRequestFromViewModel<ExampleRequest>(this, viewModel)
    .WithCancellation(CancellationToken.None)
    .DispatchAsync().To<ExampleResponse>();

It is also possible to create new cancellation scopes with the following syntax:

await cancellationContext.ScopeAsync(async () => {
    await interaction.DispatchAsync(
        new ExampleRequest { Value = 123 }
    );
    await interaction.DispatchAsync(
        new ExampleRequest { Value = 456 }
    );
}, CancellationToken.None);

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
97.4% Coverage on New Code
0.1% Duplication on New Code

See analysis details on SonarQube Cloud

[trickyward]

Changes look good to me.