remove array from the columnInfo and FieldType

[YangKeao]

Revert #317.

It's fine to just delete the array field, as both the tikv/tikv#15537 and pingcap/tidb#46718 are not merged, and the array field is not used in tidb and tikv.

I also left a comment to avoid reusing the field id (though it's not a big problem to reuse the id of array, because they are not used in any released version).

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