Fix memory read error in get_dremel_data in page_enc.cu

[davidwendt]

Reference issue #8883 and depends on PR #8884

The PARQUET_TEST fails with cuda-memcheck when called with the rmm_mode=cuda parameter. The 4-byte read error is caused by this code logic:

// Scan to get distance by which each offset value is shifted due to the insertion of empties
auto scan_it = cudf::detail::make_counting_transform_iterator( column_offsets[level],
  [off = lcv.offsets().data<size_type>()] __device__(auto i) -> int { return off[i] == off[i + 1]; });
rmm::device_uvector<size_type> scan_out(offset_size_at_level, stream);
thrust::exclusive_scan(rmm::exec_policy(stream), scan_it, scan_it + offset_size_at_level, scan_out.begin());

The scan_it lambda will read one offset value passed the end due to the off[i + 1] statement. The exclusive_scan does not actually use the last element so the code was modified to just return false if the index, i is greater than or equal to the size of the offsets column.

[codecov]

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[devavret]

I thought hard but there's really no other easy way to achieve this.

[davidwendt]

@gpucibot merge