feat: Add native support for max_by and min_by

[pchintar]

Which issue does this PR close?

Closes #3841 .

Rationale for this change

This change adds native support for MAX_BY and MIN_BY.

These aggregates are commonly used in grouped queries. Without native support, they fall back, which prevents execution from staying within Comet’s aggregation pipeline. This change enables them to run natively and align their behavior with Spark.

What changes are included in this PR?

• Added a native implementation for max_by and min_by (maxmin_by.rs) using a shared design

  • maintains the current best (value, ordering) pair per group
  • updates and merges state using ordering comparison
  • single-pass execution with constant state per group

• Implemented GroupsAccumulator support to integrate with Comet’s grouped aggregation path

  • avoids scalar accumulation and per-row overhead
  • includes specialized handling for primitive, byte/string, and struct ordering types, with a row-based fallback for general cases
  • enables execution through CometHashAggregate for grouped workloads

• Added serialization and planner wiring

  • proto definitions for MaxBy / MinBy
  • Spark-side serde (CometMaxBy, CometMinBy)
  • registration in QueryPlanSerde
  • planner support to construct the native aggregate

• Extended operator support

  • enabled execution under HashAggregate
  • added support for SortAggregateExec where selected by Spark
  • ensured both partial and final aggregation stages execute natively

How are these changes tested?

Validated against Spark for:

• grouped and non-grouped queries
• null handling (both ordering and value)
• tie behavior (equal ordering selects the latest value)
• struct ordering
• both hash and sort aggregate plans

Results match Spark semantics, and supported queries execute without any fallback.

Note: I've made the two changes required: 1)Updating the title correctly & 2)Adding the Licence header for maxmin_by.rs

[pchintar]

Hi, so I understand the issue with the formatting of rust files & so I ran cargo fmt --all to address the lint failure. But I don't know what's causing the remaining few couple of errors?

[coderfender]

@pchintar , you would want to download the logs and grep for FAILED and see which particular spark tests failed and fix code accordingly