(ecs-patterns): QueueProcessingFargateService - Allow task role to be specified

Allow the `Role` used by the `Task` created by the service to be specified in configuration

### Use Case
Allow for customization of the `Role` such as setting the role name.

### Proposed Solution

I'm torn here. What is really needed is come consistency between the ECS patterns when it comes to configuration. ApplicationLoadBalancedFargateService provides an imageOptions configuration property that contains an optional Role property. QueueProcessingFargateService only has an image property, so it would appear that `taskRole` would need to be defined on the configuration root.

* [ ] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

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This is a :rocket: Feature Request

Start by comparing the configuration of QueueProcessingFargateService with ApplicationLoadBalancedFargateService, focusing on how the task Role is exposed. Determine the compatible configuration shape and whether the change affects existing callers. Done means users can specify the task Role, including a custom role name, with consistent ECS pattern configuration.

Written by the indexing model from the issue text.