Lucene94HnswVectorsFormat validation fails with large segments

[jtibshirani]

I ran a test on Lucene 9.4 where I tried to force merge 2 million vectors with
dimension 768. It failed with

java.lang.IllegalStateException: Vector data length 3070061568 not matching
size=999369 * dim=768 * byteSize=4 = -1224905728

The problem is that we use an integer to represent the size, which is too small
to hold it. The bug snuck in during the work to enable int8 values, which
switched a long to an int: #1054. This error doesn't occur before version 9.4.

[jtibshirani]

Here's the stack trace:

java.lang.IllegalStateException: Vector data length 3070061568 not matching size=999369 * dim=768 * byteSize=4 = -1224905728
	at org.apache.lucene.core@9.4.0/org.apache.lucene.codecs.lucene94.Lucene94HnswVectorsReader.validateFieldEntry(Lucene94HnswVectorsReader.java:185)
	at org.apache.lucene.core@9.4.0/org.apache.lucene.codecs.lucene94.Lucene94HnswVectorsReader.readFields(Lucene94HnswVectorsReader.java:156)
	at org.apache.lucene.core@9.4.0/org.apache.lucene.codecs.lucene94.Lucene94HnswVectorsReader.readMetadata(Lucene94HnswVectorsReader.java:103)
	at org.apache.lucene.core@9.4.0/org.apache.lucene.codecs.lucene94.Lucene94HnswVectorsReader.<init>(Lucene94HnswVectorsReader.java:64)
	at org.apache.lucene.core@9.4.0/org.apache.lucene.codecs.lucene94.Lucene94HnswVectorsFormat.fieldsReader(Lucene94HnswVectorsFormat.java:157)

Thanks to @ebadyano and @benwtrent for helping me track this down so quickly.