[FEA] index_in_list() to return the index of a search-key in a list row

[mythrocks]

#7039 added a lists::contains() function to test whether each list row contains a specified search-key. This works with scalar search-keys and with columns, and returns a column of BOOL8.

It would be good to have a lists::index_in_list() that functions similarly, to return the index of the specified search-key in each list row. E.g.

using lcw         = tests::lists_column_wrapper<int32_t>;
auto lists        = lcw{{0,1,2,3}, {4,5,6,7}, {8,9,0,1}};
auto s_key        = make_int_scalar(1);
auto index_column = lists::index_in_list(lists, s_key); // {1, -1, 3};

Such a function would be useful in implementing a GPU accelerated array_position() in SparkSQL.

[mythrocks]

One might also use this to look up a map column (implemented, say, as a LIST<STRUCT<key,value>>:

1. Extract keys as a LIST<key>, and values as a LIST<value>, (accounting for nulls, etc.)
2. Compute index_in_list(search_key) on the keys column. This returns the position of search_key in each list row.
3. Compute extract_list_element(values, indices) to extract the indices[i]th element from each list row.

[github-actions]

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