`Column::from_qualified_name` result is potentially feature-set dependent

`Column::from_qualified_name` uses different implementation of `parse_identifiers_normalized` / `parse_identifiers` depending on whether `sql` feature is enabled.

It is assume that these implementation are behaviorally different, or may be different in the future.

Let's now consider a crate X that uses DataFusion with `sql` feature disabled and it depends on particular behavior of `Column::from_qualified_name`.

If the crate is used in a bigger project which causes `sql` feature to be enabled, the result is unpredictable to X. The app may not work correctly even though each component works and all its tests pass.

Start at Column::from_qualified_name and trace its feature-gated calls to parse_identifiers_normalized and parse_identifiers with sql enabled and disabled. Determine the intended invariant and add coverage for both configurations; done means the result no longer changes unexpectedly with the sql feature.

Written by the indexing model from the issue text.