Optimized translation for indexing of JSON primitive collections

[roji]

#30426 is adding the ability to query into JSON collections. Indexing (AKA ElementAt) is supported, but currently is translated to SQL subquery syntax; while this is the right thing for relational (will work on any provider), most databases have a specific syntax for indexing into a JSON array: SQLite has the ->> operator, while with SQL Server we should be able to use CROSS APPLY with OPENJSON.

[roji]

Also, optimize JsonScalarExpression within OpenJson/json_each, so that instead of:

OpenJson(JSON_VALUE([t].[Owned], '$.Strings'))

We get:

OpenJson([t].[Owned], '$.Strings')

(see test Column_collection_inside_json_owned_entity)