Add test case links to e2e shared examples

Désirée Chevalierrequested to merge
qa-add-testcases-to-shared-example-e2e-specs into master

What does this MR do and why?

Adds test case links to e2e shared examples and templated specs to reduce load on test reporting.

Part of https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/630 and gitlab-qa#662 (closed)

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