Pattern match comparisons and generate PostgreSQL row value comparisons

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PG supports (x, y) > (1, 2), which is the same as x > 1 || x == 1 && y > 2. We can pattern-match the latter and simplify it to the former.

For background, this is particularly useful for keyset pagination with multiple columns.

Not sure if the simplification has actual benefits beyond prettier SQL - but this is a weekend project for playing around with expression trees :)

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Assuming we do something in dotnet/efcore#26822, this should be reverted.

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I am reverting this. As per dotnet/efcore#26822 (comment), the right way for users to specify this is via C# tuple syntax - even if that isn't supported today (except maybe via explicit new ValueTuple(..)). The pattern matching approach here will probably miss various tree shapes, and if it's released it would be problematic to remove it later.

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Note: #2349 represents a better approach to this.