Add aliasing to create named tuples

[BenoitRanque]

Our generated SQL casts anonymous tuples to named tuples at the very top:

-- cast the anonymou tuple to a named tuple, relying on position
SELECT cast(
  _rowset._rowset,
  'tuple(foo String, bar String)'
) FROM (
  -- create anonymous, positional tuple
  -- starting in 24.7, creates a named tuple with fields _field_foo and _field_bar
  SELECT tuple(
    _row._field_foo,
    _row._field_bar
  ) AS _rowset
  FROM (
    SELECT
      -- fields aliased with a namespace
      -- required as we may select fields for other reasons
      -- (eg. ordering, relationships) 
      'foo' AS _field_foo,
      'bar' AS _field_bar
  ) AS _row
) AS _rowset

The above fails starting in ClickHouse 24.7 due to a breaking change:

Function tuple will now try to construct named tuples in query (controlled by enable_named_columns_in_function_tuple). Introduce function tupleNames to extract names from tuples.

This manifests is a very weird way: when casting, we end up getting the default value for the data type, because we cannot fetch the correct column in the tuple.

Turns out, it's possible to alias fields when creating a named tuple, to set the names for the tuple:

-- casting now works
SELECT cast(
  _rowset._rowset,
  'tuple(foo String, bar String)'
) FROM (
  -- create a named tuple
  SELECT tuple(
    _row._field_foo as foo,
    _row._field_bar as bar
  ) AS _rowset
  FROM (
    SELECT
      'foo' AS _field_foo,
      'bar' AS _field_bar
  ) AS _row
) AS _rowset

[codedmart]

This above is just a format change right?

[BenoitRanque]

mostly formatting yes. there's an actual change at the bottom, and I guess cargo decided that warranted a reformat