[FEA] Refactoring JSON reader tree algorithms in 24.08 about cudf HOT 2 OPEN

Hello @shrshi, I added this issue about the refactoring work you started this week. Please excuse me if you documented this elsewhere and I missed it. Please feel free to update these topics with your current picture of the project. Thank you!

from cudf.

Tree representation:

This feature introduces a new column_tree_csr struct that stores the column tree representation in CSR format. The nodes are renumbered level-wise instead of being directly mapped to column ids. This serves two purposes - (i) sub-trees matching input dtype schema can be skipped in between-column pruning, and (ii) sub-trees matching non-conforming dtypes in mixed type columns can be similarly skipped (within-column pruning).
The key advantage of wrapping column properties - mixed types and map types support, column pruning, ignoring null literals, column validity, and array of arrays support - as 'non-zero' values in column_tree_csr struct is maintainability and ease of adding new features in the future.

from cudf.