[Automation] - Use testid locators rather than positional on pagination

[izaac]

Summary

Fixes rancher/qa-tasks#1388

Positional locators aren't recommended and is a red flag on automation. Those shouldn't be used under any circumstance and is something commonly used as last resort.

Occurred changes and/or fixed issues

Added data-testid for pagination navigation buttons.

Areas or cases that should be tested

Automation is only affected and this isn't a functional change in the Vue code.

Test done: Cluster Pagination tests executed and passed.

Checklist

• The PR is linked to an issue and the linked issue has a Milestone, or no issue is needed
• The PR has a Milestone
• The PR template has been filled out
• The PR has been self reviewed
• The PR has a reviewer assigned
• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[yonasberhe23]

LGTM