E2E: Group Settings Billing Page data-testid Migration

What does this MR do and why?

Relates to gitlab-org/quality/quality-engineering/team-tasks#1931 (closed) and gitlab-org/quality/quality-engineering/team-tasks#1735

In order to better unify our E2E testing framework with lower level tests, this MR migrates the data-qa-selectors to data-testids in the Gitlab::Page::Group::Settings::Billing page. This also includes cleanup of selectors no longer in use by our E2E tests.

How to set up and validate locally

Unfortunately, the E2E tests that use these selectors can only be run against Staging at this time. If there is a particular E2E test you would like to verify locally (and you have a local CustomersDot instance setup and configured) feel free to let me know and I can help walk you through ways on how to do that to verify the specific selectors that were changed.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.