Kotlin/dataframe

AI Summary: The task involves refactoring the Kotlin DataFrame library's selection DSL. Specifically, it requires removing the default predicate from the `cols()` function, adding overloads that use `all()` and `allCols()` instead, and deprecating the old `cols()` function with appropriate messaging to guide users to the new, more expressive and compiler-plugin-compatible alternatives.

AI Summary: The task is to implement Jupyter code generation for the `Pivot` type in the Kotlin DataFrame library. This involves ensuring that when a `pivot` operation is performed on a DataFrame within a Jupyter Notebook environment, the resulting DataFrame's columns are correctly accessible in subsequent code cells. The solution should mirror the approach used to resolve a similar issue (https://github.com/Kotlin/dataframe/issues/1221).

AI Summary: The task requires adding support for Apache Arrow's TimeStampTZ vectors to the Kotlin DataFrame library. This involves handling timestamps with time zone information in addition to existing timestamp support, likely requiring modifications to data reading, writing, and internal representation within the DataFrame.