[SPARK-55754][PYTHON][TEST][FOLLOWUP] Fix pure_ints type mismatch in bench

### What changes were proposed in this pull request?

Refactor `MockDataFactory.NAMED_TYPE_POOLS` in `python/benchmarks/bench_eval_type.py` so the `pure_ints`, `pure_floats`, and `pure_strings` entries reuse the corresponding `TYPE_REGISTRY` entries instead of duplicating their factory lambdas.

### Why are the changes needed?

`NAMED_TYPE_POOLS[\"pure_ints\"]` declared the column as `IntegerType()` (32-bit) but generated data with `np.int64`. Because every benchmark that uses this pool runs through serializers with `arrow_cast=True`, the mismatch was silently corrected by a 64-to-32 narrowing cast inside the pandas/arrow conversion path -- meaning the `pure_ints` scenario in seven mixins (`ArrowBatchedUDF`, `ArrowUDTF`, `ArrowTableUDF`, `MapArrowIterUDF`, `MapPandasIterUDF`, `ScalarArrowUDF`, `ScalarPandasUDF`) was measuring an extra narrowing step rather than a pure int32 baseline.

`pure_floats` and `pure_strings` had no such mismatch but duplicated the same lambdas as `TYPE_REGISTRY[\"double\"]` / `TYPE_REGISTRY[\"string\"]`, risking drift in future edits. Reusing the registry entries eliminates the duplication. `pure_ts` is left as-is because no matching `TYPE_REGISTRY` entry exists.

### Does this PR introduce _any_ user-facing change?

No. Test-only change in the benchmark module.

### How was this patch tested?

- Confirmed `NAMED_TYPE_POOLS[\"pure_ints\"][0]` now produces a `pa.int32()` array matching its `IntegerType()` declaration (was `pa.int64()`).
- Confirmed `pure_floats` and `pure_strings` still produce `pa.float64()` and `pa.string()` arrays after the refactor.
- Ran `setup` + `time_worker` for the `pure_ints` scenario across all seven affected `*TimeBench` classes; all passed.

### Was this patch authored or co-authored using generative AI tooling?

Yes. Generated-by: Claude Code (claude-opus-4-7)

Closes apache#56169 from viirya/SPARK-55724-pure-ints-followup.

Authored-by: Liang-Chi Hsieh <viirya@gmail.com>
Signed-off-by: Liang-Chi Hsieh <viirya@gmail.com>

Author: viirya

python/benchmarks/bench_eval_type.py

@@ -261,11 +261,9 @@ class MockDataFactory:
 
     NAMED_TYPE_POOLS: dict[str, list[tuple[Callable, Any]]] = {
         "mixed": MIXED_TYPES,
-        "pure_ints": [
-            (lambda r: pa.array(np.random.randint(0, 1000, r, dtype=np.int64)), IntegerType())
-        ],
-        "pure_floats": [(lambda r: pa.array(np.random.rand(r)), DoubleType())],
-        "pure_strings": [(lambda r: pa.array([f"s{j}" for j in range(r)]), StringType())],
+        "pure_ints": [TYPE_REGISTRY["int"]],
+        "pure_floats": [TYPE_REGISTRY["double"]],
+        "pure_strings": [TYPE_REGISTRY["string"]],
         "pure_ts": [
             (
                 lambda r: pa.array(