Use (valueCount + 1) * OFFSET_WIDTH instead of offsetAllocationSizeInBytes

Addresses review feedback from bodduv: LargeListVector.clear() sets
offsetAllocationSizeInBytes = offsetBuffer.capacity(), which is 0 after
the buffer is released. Using offsetAllocationSizeInBytes would allocate
a 0-byte buffer in that case.

(valueCount + 1) * OFFSET_WIDTH is always the correct minimum size
(at least OFFSET_WIDTH when valueCount == 0) and matches the writerIndex
that setReaderAndWriterIndex() just set.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Change-Id: Iae6b0a2578deb0f7fd8ca7ae36a0a7e3fc595765

Author: prashanthbdremio

vector/src/main/java/org/apache/arrow/vector/complex/LargeListVector.java

@@ -280,7 +280,7 @@ public List<ArrowBuf> getFieldBuffers() {
     if (offsetBuffer.capacity() == 0 && offsetBuffer.writerIndex() > 0) {
       long writerIdx = offsetBuffer.writerIndex();
       offsetBuffer.getReferenceManager().release();
-      offsetBuffer = allocateOffsetBuffer(offsetAllocationSizeInBytes);
+      offsetBuffer = allocateOffsetBuffer((long) (valueCount + 1) * OFFSET_WIDTH);
       offsetBuffer.writerIndex(writerIdx);
     }
     result.add(offsetBuffer);

vector/src/main/java/org/apache/arrow/vector/complex/ListVector.java

@@ -238,7 +238,7 @@ public List<ArrowBuf> getFieldBuffers() {
     if (offsetBuffer.capacity() == 0 && offsetBuffer.writerIndex() > 0) {
       long writerIdx = offsetBuffer.writerIndex();
       offsetBuffer.getReferenceManager().release();
-      offsetBuffer = allocateOffsetBuffer(offsetAllocationSizeInBytes);
+      offsetBuffer = allocateOffsetBuffer((long) (valueCount + 1) * OFFSET_WIDTH);
       offsetBuffer.writerIndex(writerIdx);
     }
     result.add(offsetBuffer);