Improve `RunLengthBitPackingHybridDecoder.readNext` to avoid per-call buffer allocation and `DataInputStream` wrapping

### Describe the enhancement requested

`RunLengthBitPackingHybridDecoder.readNext()` allocates a new `int[]` and `byte[]` on every PACKED-mode call. In workloads that decode many bit-packed runs (definition levels, repetition levels, RLE-encoded integers), these allocations dominate the read-side allocation profile. The upstream code even acknowledges this with a `// TODO: reuse a buffer` comment.

### Problem 1: per-call buffer allocation

[Lines 94–95](https://github.com/apache/parquet-java/blob/4c8f4d4b/parquet-column/src/main/java/org/apache/parquet/column/values/rle/RunLengthBitPackingHybridDecoder.java#L94-L95) allocate fresh arrays on every PACKED-mode `readNext()`:

```java
currentBuffer = new int[currentCount]; // TODO: reuse a buffer
byte[] bytes = new byte[numGroups * bitWidth];
```

`currentCount` is always `numGroups * 8`, and `numGroups` is typically small (1–16 groups = 8–128 values per run). These allocations are individually modest but occur thousands of times per column chunk — once per bit-packed run. In a 180M-row merge with multiple integer/boolean columns, the cumulative allocation is substantial.

Since `currentCount` varies between runs (different `numGroups` values), the fix retains the field-level `int[]` and a new field-level `byte[]`, growing them only when the next run requires a larger buffer.

### Problem 2: per-call DataInputStream wrapping

[Line 98](https://github.com/apache/parquet-java/blob/4c8f4d4b/parquet-column/src/main/java/org/apache/parquet/column/values/rle/RunLengthBitPackingHybridDecoder.java#L98) creates a `new DataInputStream(in)` on every PACKED-mode call:

```java
new DataInputStream(in).readFully(bytes, 0, bytesToRead);
```

This allocates a `DataInputStream` wrapper object per call just to access `readFully()`. A private `readFully()` method on the decoder itself eliminates this allocation and the virtual dispatch through the wrapper.

### Component(s)

Core

Commencez dans parquet-column/src/main/java/org/apache/parquet/column/values/rle/RunLengthBitPackingHybridDecoder.java, en vous concentrant sur le chemin PACKED-mode de readNext() autour des lignes 94–98 et sur le TODO existant. Suivez l’utilisation des buffers et des lectures d’entrée, puis exécutez les tests pertinents du décodeur. Le travail est terminé lorsque les appels répétés en PACKED-mode réutilisent des buffers de taille suffisante sans créer de wrappers DataInputStream à chaque appel, tout en préservant le comportement du décodage.

Rédigé par le modèle d'indexation à partir du texte de l'issue.