Fix TableScan to generate correct partition bucket paths

[luoyuxia]

Parent Issue

Part of #124 (support partitioned table)
Depends on #126 (BinaryRow deserialization), #127 (partition path generation)

Background

TableScan::plan_snapshot() currently discards partition information when building DataSplits:

// table_scan.rs:154
for ((_partition, bucket), group_entries) in groups {
    // ...
    // table_scan.rs:171-173
    // todo: consider partitioned table
    let bucket_path = format!("{base_path}/bucket-{bucket}");
    let partition = BinaryRow::new(0);  // Always empty!
}

For partitioned tables, the correct path should be {table_path}/{partition_path}/bucket-{bucket}, e.g., {table_path}/dt=2024-01-01/bucket-0/.

What needs to be done

1. Pass partition type info to plan_snapshot()

   • Add partition keys (names) and partition field types (from TableSchema) as parameters, or pass the TableSchema itself
   • Alternatively, change plan_snapshot() from a static method to an instance method that can access self.table.schema

2. Decode partition bytes into BinaryRow

   • For each group key (partition_bytes, bucket), construct a BinaryRow from the raw bytes using BinaryRow::from_bytes(arity, data)
   • The arity is the number of partition keys

3. Generate partition path using PartitionPathUtils

   • Call the partition path utility (from Implement partition path generation (PartitionPathUtils) #127) to compute the partition path segment
   • Construct bucket_path as {table_path}/{partition_path}/bucket-{bucket}

4. Store actual partition data in DataSplit

   • Pass the decoded BinaryRow (with real data) to DataSplitBuilder.with_partition() instead of the empty BinaryRow::new(0)

Affected files

• crates/paimon/src/table/table_scan.rs — plan_snapshot() method

[luoyuxia]

Merged into a combined issue with #129 and #130