[ECR] [Lifecycle policies]: Enable tagPrefixList regex and exceptions

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**Tell us about your request**
What do you want us to build?

- Exceptions for lifecycle policies
- tagPrefixList regex support for lifecycle policies

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

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

**Are you currently working around this issue?**
How are you currently solving this problem?
I use fine-grained policies with tagPrefixList but it minimizes the results overall my repos.

**Additional context**
Anything else we should know?

**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.)

Start with the ECR lifecycle policies request in this issue, focusing on tagPrefixList regex support and policy exceptions. No repository files, tests, or implementation entry points are identified; clarify the expected matching and exception behavior with maintainers. Done means both requested capabilities address the reported repository filtering limitation.

Written by the indexing model from the issue text.