Strip replica labels from series in Store Gateway

[fpetkovski]

Store Gateway is currently the only store which does not strip replica labels from stores. This causes deduplication problems for certain cases where users need to deduplicate by labels stored in TSDB.

This commit modifies store-gateway to strip replica labels when they are also stored in TSDB blocks.

This is a partial fix for #6257.

• I added CHANGELOG entry for this change.
• Change is not relevant to the end user.

Changes

Verification

[GiedriusS]

Isn't this already done at https://github.com/thanos-io/thanos/pull/5988/files#diff-3e2896fafa6ff73509c77df2c4389b68828e02575bb4fb78b6c34bcfb922a7ceR879?

[fpetkovski]

That PR only removes replica labels from external labels, but I thought we should also strip when they are part of the series. At least this is what we do for the receiver and sidecar.

However, after my last comment, I think this would only mask the dedup problem that people are seeing in 0.31.0 and solve only a subset of issues.

[stale]

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[douglascamata]

@fpetkovski I rebased this with the tests from main and it solved the problem in the Store GW. Problem's still present in Receive and Sidecar. Do you think you can extend the fix here to these other components?