fix(blooms): Fix findGaps when ownership goes to MaxUInt64 and that is covered by existing meta

[salvacorts]

What this PR does / why we need it:

If a meta and ownership tange covers till the end of the FP key-space (MaxUInt64), the current implementation of findGaps overflows and the keyspace covered by that meta is misreported as a gap:

loki/pkg/bloomcompactor/controller.go

Line 738 in 4c88be0

leftBound = min(clippedMeta.Max+1, ownershipRange.Max+1)

In more detail:

loki/pkg/bloomcompactor/controller.go

Lines 738 to 756 in 4c88be0

	leftBound = min(clippedMeta.Max+1, ownershipRange.Max+1)
	// since we've already ensured that the meta is within the ownership range,
	// we know the xor will be of length zero (when the meta is equal to the ownership range)
	// or 1 (when the meta is a subset of the ownership range)
	xors := searchRange.Unless(*clippedMeta)
	if len(xors) == 0 {
	// meta is equal to the ownership range. This means the meta
	// covers this entire section of the ownership range.
	continue
	}
	gaps = append(gaps, xors[0])
	}
	if leftBound <= ownershipRange.Max {
	// There is a gap between the last meta and the end of the ownership range.
	gaps = append(gaps, v1.NewBounds(leftBound, ownershipRange.Max))
	}

If we only have one meta spanning the whole keyspace:

• leftBound = min(clippedMeta.Max+1, ownershipRange.Max+1) Here clippedMeta.Max is MaxUint64 so +1 makes this 0
• if len(xors) == 0 { is true so we end the loop
• if leftBound <= ownershipRange.Max { since leftBound is 0 we get inside here and add the gap.

This PR fixes this by taking care of the overflows.

Which issue(s) this PR fixes:
Fixes #12499

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• For Helm chart changes bump the Helm chart version in production/helm/loki/Chart.yaml and update production/helm/loki/CHANGELOG.md and production/helm/loki/README.md. Example PR
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[chaudum]

lgtm