Rescoring consist of recalculating similarity score and reordering results based on it.
In this patch we add calculation of similarity score as a hidden (non-serialized) column and following patch will add reordering.
Normal ordering uses `add_column_for_post_processing`, however this works only for regular columns, not function.
So we create it together with user requested columns (this also forces the use of `selection_with_processing`) and hide the column later.
This also requires special handling for 'SELECT *' case - we need to manually add all columns before adding similarity column.
In case user already asks for similarity score in the SELECT clause, this value will be calculated twice - is should be optimized in future patches.
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