fix(compaction): fix compatible for vnode partition

[Little-Wallace]

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What's changed and what's your intention?

#12534 will compact normal non-overlapping level to partitioned level.
But we check whether a level need to be compacted to partitioned level by check the variable of structure Levels.
If this cluster upgraded from an old version, the variable vnode_partition_count of Levels would never be changed, and we will treat it as a no-partitioned group.

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