Move tests to microservices_mode integration package

[friedrichg]

What this PR does: Move microservices_mode tests to separate thread in GitHub Actions

Checklist

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

[yeya24]

Can you explain what this PR is for?

Tbh I feel those test cases are quite flaky and it is very complicated right now. I wonder if we really need to test every combination of index cache backend, chunk cache backend and bucket index enabled or not.

[friedrichg]

@yeya24
Before
https://github.com/cortexproject/cortex/actions/runs/21836985484/usage

After
https://github.com/cortexproject/cortex/actions/runs/21846216279/usage
This PRs creates a separate machine that only runs this TestQuerierWithBlocksStorageRunningInMicroservicesMode

I didn't change them in any way. Just moved them to a separate place to be run separately

[friedrichg]

Tbh I feel those test cases are quite flaky and it is very complicated right now. I wonder if we really need to test every combination of index cache backend, chunk cache backend and bucket index enabled or not.

We should remove tests without bucket index enabled. That is always a bad idea. Let's do that in separate PR