Sqlite: transform CROSS APPLY to projection when possible

[roji]

Consider the following query, where Contacts is mapped to a JSON column:

_ = context.Clients
    .Select(c => new ClientDto
    {
      Id = c.Id,
      Name = c.Name,
      Contacts = c.Contacts.Select(contact => new ContactDto
      {
        FirstName = contact.FirstName,
        LastName = contact.LastName,
        Address = contact.Address,
        Email = contact.Email,
        PhoneNumber = contact.PhoneNumber
      }).ToList()
    });

EF translates the inner Select to a CROSS APPLY, with OPENJSON (on SQL Server) to extract the JSON data as relational for materialization:

SELECT [c].[Id], [c].[Name], JSON_VALUE([c0].[value], '$.FirstName'), JSON_VALUE([c0].[value], '$.LastName'), JSON_VALUE([c0].[value], '$.Address'), JSON_VALUE([c0].[value], '$.Email'), JSON_VALUE([c0].[value], '$.PhoneNumber'), [c0].[key]
FROM [Clients] AS [c]
OUTER APPLY OPENJSON([c].[Contacts], '$') AS [c0]
ORDER BY [c].[Id], CAST([c0].[key] AS int)

This fails on SQLite, because CROSS/OUTER APPLY isn't supported there.

If the CROSS APPLY is only referenced in the projection (and not e.g. in a filter), then it should be able to transform the query to replace the CROSS APPLY with a projection subquery instead. This seems particularly useful around SQLite JSON processing, as above.

Note the similarity with #34256, where we do the opposite, lifting a subquery projection to CROSS APPLY on SQL Server (where an aggregate function is involved).

Initially raised in #34367