Leetcode 2252. Dynamic Pivoting of a Table

Given a mutable table of records, support dynamic "pivot" operations that reorient the table by grouping on a chosen column and computing aggregate metrics (counts/sums) across the other dimensions, while also handling updates and queries. The challenge is to maintain and update these grouped aggregations and the pivoted layout efficiently under frequent pivot changes and record updates, typically requiring incremental indexing or balanced/hash-based aggregation structures.