Box Query in Cte

[MazterQyou]

Cte is the only struct that has Query unboxed; all other instances are Boxed. I propose Boxing Query in Cte for the sake of interoperability and keeping things similar, thus the PR contains the proposed change.

[coveralls]

Pull Request Test Coverage Report for Build 2848948795

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.001%) to 85.446%

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Totals
Change from base Build 2848542264:	0.001%
Covered Lines:	9499
Relevant Lines:	11117

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💛 - Coveralls

[alamb]

This change is fine with me, however, there is already some discussion about un Boxing the Query in Statement 🤔

#556

cc @ever0de and @andygrove

[alamb]

The conclusion from #556 is that Boxing is the pattern and we will stick to it.