[VL] Spark 4.1: Support memory shuffle spill by size threshold (SPARK-49386)

## Backend
VL (Velox)

**Gluten version**: main branch

## Description

Spark 4.1 introduced memory-based shuffle spill thresholds (SPARK-49386, JIRA type: Improvement). The new `spillSizeThreshold` parameter enables spilling by data size rather than only by row count. Gluten's shuffle implementation does not support this threshold.

Spark 4.1 only.

**Parent issue**: #11910 (`[VL] Spark 4.x: Tracking new feature support`)

### Impact

| Suite | Exclude | spark40 | spark41 |
|-------|---------|:-------:|:-------:|
| GlutenDataFrameWindowFunctionsSuite | SPARK-49386 spill | 🟢 | 🔴 |
| GlutenJoinSuite | SPARK-49386 SortMergeJoin spill | 🟢 | 🔴 |

Note: `GlutenSQLWindowFunctionSuite` has a pre-existing spill issue ("low buffer spill threshold") unrelated to SPARK-49386 — out of scope for this issue.

### References

- Apache Spark JIRA: [SPARK-49386](https://issues.apache.org/jira/browse/SPARK-49386)

Start by reading Apache Spark SPARK-49386 and the parent tracking issue #11910, then trace Gluten's Velox shuffle implementation for the Spark 4.1 path. Use GlutenDataFrameWindowFunctionsSuite and GlutenJoinSuite to reproduce the excluded spill cases; done means both Spark 4.1 cases pass without changing the unrelated window-function spill issue.

Written by the indexing model from the issue text.