RFC: Add integration test for etcd

[ChinYing-Li]

What this PR does:
Adds one integration test for etcd.
Signatures of six functions used in the integration tests had been changed.
I believe we should also test compactor, store gateway and ruler that use etcd as ring backend (hence the signature of NewRuler, NewCompactor etc. should also be modified), but I'd like to have some early feedback before moving forward.

Questions:

1. Currently, in the backward compatibility tests, only consul is used. Shall backward compatibility test cases for etcd be added as well?

Which issue(s) this PR fixes:
Fixes #2137

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pstibrany]

Can you please take a look at failed linter checks? https://github.com/cortexproject/cortex/pull/4113/checks?check_run_id=2431082044

Thank you!

[ChinYing-Li]

One irrelevant test is failing; do we need to kick the CI again?

[ChinYing-Li]

@pstibrany A gentle ping; A test that seems irrelevant fails. Thanks!

[pstibrany]

I don't seem to be able to restart checks here, not sure why. Can you try to push empty commit to your branch instead? That will trigger new run of checks. Thanks!

[ChinYing-Li]

The integration test fails in CI probably because I have changed the signature of several New* functions in integration/e2ecortex/service.go, and those changes are not in the build in the docker image used for CI.
The documentation says that the PR code is build in the image, and the integration test succeeds on my machine.
I will investigate why it's failing CI.
Updates:
Now I've resolved the CI failure, PR ready for review. Thank you, and any suggestion is appreciated.
@pstibrany

[ChinYing-Li]

PR ready for review, and any suggestion is appreciated! @pstibrany

[stale]

This issue has been automatically marked as stale because it has not had any activity in the past 60 days. It will be closed in 15 days if no further activity occurs. Thank you for your contributions.

[bboreham]

Thanks for the PR; sorry it has sat around such a long time.
The "chunks" storage has been deprecated, so this test would be deleted at some point.
Can it be modified to use "blocks" storage?

[ChinYing-Li]

Hi, sorry for getting back late; was a bit tied down by the recruiting season. I have introduced the integration/block_storage_backends_test.go, which contains one test case.
Any suggestion is appreciated!

[ChinYing-Li]

@bboreham Just a ping to let you know I've updated the PR to use block storage. Thank you!

[bboreham]

I might have packaged up store RingStore, address string into a struct to reduce the boilerplate at all call-sites, but it's fine as-is.
Thanks!