[v2 Bug] Fusion dbt-agate panic: index_of_value_in_column via dbt_utils.get_query_results_as_dict()

Fusion dbt compile panics on models using dbt_utils.get_query_results_as_dict():

panic: not yet implemented: index_of_value_in_column (crates/dbt-agate/src/table.rs:250)

Reproduced on Fusion previews 218, 219, and 220. The panic is reached through Column.values().index() / dictionary-building in the macro.

The proposed fix implements TableRepr::count_occurrences_of_value_in_column and TableRepr::index_of_value_in_column using cell(), adjusted_column_index(), and Value equality, with unit coverage for integer/string columns, negative indices, missing values, and counts.

The underlying unimplemented methods are visible here: the todo!() implementations.