`collectionStats` query fully implemented

[kidunot89]

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What does this implement/fix? Explain your changes.

• Fixes regressions created by WPGraphQL v1.24.x
• Fixes collectionStats query parameters
• Adds attributes field to the *ToProductUnionConnectionWhereArgs input types
• Deprecates attribute and attributeTerm on the *ToProductUnionConnectionWhereArgs input types
• Requires collectionStats query and attributes field functionality introduced in WooCommerce v3.9.0

Does this close any currently open issues?

Resolves #845

Any relevant logs, error output, GraphiQL screenshots, etc?

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Any other comments?

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Where has this been tested?

• WooGraphQL Version: …
• WPGraphQL Version: …
• WordPress Version:
• WooCommerce Version: