Create flaky report for end-to-end tests
It would be useful having a flaky report for end-to-end tests, as we have for RSpec tests.
This report can be used together with other approaches, for example, to de-quarantine a quarantined test.
For an example of the RSpec flaky report, see https://gitlab.com/gitlab-org/gitlab-ce/issues/45044#note_208071511.
This issue is being created as a follow-up based on this Slack discussion: https://gitlab.slack.com/archives/C3JJET4Q6/p1568238262215900?thread_ts=1568226002.213500&cid=C3JJET4Q6.