loki Storage: Fix `max_chunks_per

What this PR does / why we need it: There are some issues that max_chunks_per_query isn't working on limiting the chunks per query.

#9101
#11077

I found that max_chunks_per_query is now totally unused configuration. I found that max_chunks_per_query was using before #5650 and #5833. On those refactoring pr, limiting chunks per query logic had to move on CompositeStore, but it was missing. I think it's pretty important configuration to limit memory. So I write max_chunks_per_query logic on composite_store.go and test.

I do some works below:

Add the limit logic just before that CompositeStore returns chunks. (CompositeStore.GetChunks) I referred the code before #5650 and #5833.
Remove unused cortex util code.

Which issue(s) this PR fixes: Fixes #9101

Special notes for your reviewer: It's the first time to open pr on open source community for me. I'm newbie with Loki. Please correct me if I'm wrong 😁 Thank you

@cyriltovena @owen-d Could you check my pull request?

Checklist

[x] Reviewed the CONTRIBUTING.md guide (required)
[ ] Documentation added
[x] Tests updated
[ ] CHANGELOG.md updated
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[ ] Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
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