Add index stats info to bucket index

[yeya24]

What this PR does:

We added Index Stats info to the meta.json file and use that to estimate series and chunk size. However, when store gateway uses bucket index, it won't actually download meta.json file from object store. It will generate meta.json file from the information provided by bucket index.

This pr adds additional fields series_max_size and chunk_max_size to bucket index per block to help address this issue. The change is also backward compatible from what I tested.

Which issue(s) this PR fixes:
Fixes #

Checklist

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

[friedrichg]

LGTM

[yeya24]

The issue of current implementation is that, for old blocks in the bucket index, we don't update series_max_size and chunk_max_size fields because bucket index updater just copies what we have from the old bucket index.
Only those new blocks that don't appear in bucket index will be added with those fields

[alanprot]

The issue of current implementation is that, for old blocks in the bucket index, we don't update series_max_size and chunk_max_size fields because bucket index updater just copies what we have from the old bucket index.
Only those new blocks that don't appear in bucket index will be added with those fields

This should be fine for this PR?

[yeya24]

This should be fine for this PR?

Yeah I think it should be fine. It is another story of migration, which can be done separately.