avoid int32 overflow in BitPackedRunDecoder::GetBatch offset

[metsw24-max]

int32 overflow in the bit-packed run decoder offset
GetBatch works out the byte position with values_read_ * value_bit_width in 32-bit int. For a large bit-packed run (this decodes untrusted parquet RLE/bit-packed dictionary indices and levels, with value width up to 64) the product passes INT32_MAX and wraps negative, so bytes_fully_read goes negative and unread_data ends up before the buffer, giving an out of bounds read in unpack. raw_data_size just above already widens to int64 before the same multiply, so I matched that here.

[github-actions]

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