[FEATURE] Add RANGE_BUCKET sort mode for bulk insert to handle large datasets without OOM

## Motivation

When using bulk insert with very large datasets (e.g., billions of records, many TB of data), the existing sort modes can cause OOM issues:

- **GLOBAL_SORT**: Requires a global shuffle that can cause OOM when sorting large datasets with many files (e.g., 2800+ files each ~1GB)
- **PARTITION_SORT**: Provides suboptimal file sizes and doesn't help with record key ordering across partitions
- **NONE**: Fast but provides no data ordering benefits for query predicate pushdown

Users with 5TB+ datasets and 60+ billion records (see #12116) have reported OOM issues with all existing sort modes.

## Proposed Solution

Add a new `RANGE_BUCKET` sort mode that:

1. **Uses quantile-based bucketing**: Leverages Spark's `approxQuantile()` algorithm to compute range boundaries with minimal memory overhead
2. **Assigns records to buckets**: Records are assigned to buckets based on value ranges of a specified column (defaulting to record key)
3. **Handles skew**: Automatically detects skewed partitions and redistributes to sub-partitions
4. **Optional within-partition sorting**: Can sort records within each bucket for better compression

### Benefits

- **Memory efficient**: Avoids expensive global shuffle operations that cause OOM
- **Better query performance**: Tight value ranges in parquet footers enable effective predicate pushdown
- **Better compression**: Adjacent records (in sorted order) are colocated, enabling ~30% better compression with dictionary/RLE encoding
- **Configurable**: Supports custom partitioning columns, skew detection thresholds, and within-partition sorting

### Proposed Configuration Options

| Config | Description |
|--------|-------------|
| `hoodie.bulkinsert.sort.mode=RANGE_BUCKET` | Enable range bucket mode |
| `hoodie.bulkinsert.range.bucket.partitioning.column` | Column to use for bucketing (defaults to record key) |
| `hoodie.bulkinsert.range.bucket.partitioning.sort.within.partition` | Enable within-partition sorting |
| `hoodie.bulkinsert.range.bucket.partitioning.skew.multiplier` | Threshold for skew detection |
| `hoodie.bulkinsert.range.bucket.partitioning.quantile.accuracy` | Accuracy for quantile computation |

## Use Case

This is particularly useful for:
- Initial bulk loading of very large datasets
- Tables with high-cardinality primary keys (UUIDs, etc.)
- Workloads where query patterns benefit from record key ordering

No files, tests, or entry points are named. Start by locating bulk-insert sort-mode handling and the existing GLOBAL_SORT, PARTITION_SORT, and NONE implementations; done means RANGE_BUCKET supports the listed configuration options, quantile-based bucketing, skew handling, and optional within-partition sorting without the reported OOM behavior.

Written by the indexing model from the issue text.