[ECR Public] [request]: add publisher-pays, unlimited pulls option for repositories

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**Tell us about your request**
I'd like to be able to opt-in repositories for unlimited pulls from unauthenticated users, where the publisher pays the cost for anything above the free tier.

**Which service(s) is this request for?**
ECR Public

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Some of the container images we publish will be used in situations where supplying credentials to authenticate access is difficult, and where the per-IP limit for data bandwidth may create an availability risk. This is especially problematic for on-prem usage where all requests may appear to originate from a small number of IP addresses because of NAT.

Examples include:
* Amazon Linux images used for automated testing
* Bottlerocket host container images used for out-of-band management of production fleets
* EKS Distro images used by EKS Anywhere to deploy clusters

In these scenarios, there's a risk that a pilot deployment on-prem will be successful, only to run into the limits as it scales out in production.

**Are you currently working around this issue?**
No, as these are new scenarios for us.

A potential workaround would be to advise customers to mirror repositories to an internal registry service so the limits would not apply. This could be desirable for other reasons, such as exercising more control over which images can be pulled, or eliminating an external network dependency.

The downside is that artifacts like Bottlerocket VM images could not be used with their default values, and would always require some site-specific configuration as a best practice. This is at odds with our goals for safe defaults and ease-of-use.

**Additional context**
This request comes from the Bottlerocket team, with support from EKS.

**Attachments**
If you think you might have additional information that you'd like to include via an attachment, please do - we'll take a look. (Remember to remove any personally-identifiable information.)

The request concerns an opt-in publisher-pays, unlimited-pulls option for ECR Public repositories. No repository files, tests, or implementation entry points are identified; begin by determining whether this roadmap repository contains an implementation surface, and consider the work done when the service supports the requested repository option.

Written by the indexing model from the issue text.