Added `array` valueType to reduce members filter code duplication
Added `array` valueType to reduce members filter code duplication

refs https://github.com/TryGhost/Team/issues/1419

- continued cleanup of filtering code
  - added `array` as a `valueType` for member filters removing the need for duplicated NQL generation code between `label` and `product` filters
  - cleaned up duplicated relation string/operator handling

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