Add v1alpha8 variant of pagination structs

[Marenz]

• Add v1alpha8 variant of pagination structs

[llucax]

So we deprecate Params and remove PaginationParams too, right?

[Copilot]

Pull Request Overview

This PR adds support for v1alpha8 variants of pagination structs to provide backward compatibility while transitioning API versions. The changes deprecate existing pagination classes in favor of new unified implementations that support both v1 and v1alpha8 protobuf message formats.

• Introduces a new PaginationInfo class that can handle both v1 and v1alpha8 protobuf messages
• Deprecates the existing Info and Params classes with appropriate migration guidance
• Adds comprehensive test coverage for both v1 and v1alpha8 pagination functionality

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/frequenz/client/common/pagination/init.py	Adds new PaginationInfo class with dual proto support and deprecates legacy classes
tests/test_pagination.py	Comprehensive test suite covering both v1 and v1alpha8 pagination variants
RELEASE_NOTES.md	Documents deprecations and new v1alpha8 pagination features

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}