scanner-status: Support both old & new scanner metrics

[vadmeste]

Depends on minio/madmin-go#227

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under the terms of the [Apache 2 license] (https://www.apache.org/licenses/LICENSE-2.0).
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Description

Old metrics is when the scanner uses cycle concept to scan all the namespace

New metrics is when we have parallel bucket scanning

Motivation and Context

How to test this PR?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here