[BUG] order of grids different when using openvdb::io::File vs openvdb::io::Stream

Windows 10
VDB 9.0
Clang 13 LLVM

When a .vdb file is opened with openvdb::io::File and iterated, the order of the names is different then when using openvdb::io::Stream and iterating.

```
openvdb::io::File file(sequence_filename);
// Open the file. This reads the file header, but not any grids.
file.open();

if (file.isOpen()) {
std::string channel_names[3];
uint32_t numChannels(0);

for (openvdb::io::File::NameIterator nameIter = file.beginName(); nameIter != file.endName(); ++nameIter)
{
channel_names[numChannels] = nameIter.gridName();
++numChannels;
}

FMT_LOG_WARN(VOX_LOG, "{:d} channels " " [{:s}] [{:s}] [{:s}]", numChannels, channel_names[0], channel_names[1],
channel_names[2]);
}
file.close();
```

and

```
std::ifstream file(frame_data.path, std::ios_base::in | std::ios_base::binary);
openvdb::io::Stream const stream(file, false); // *bugfix - parameter false, disables "delayed" loading of voxel data. If delayed-loading is on, the performance tanks! speedup++
openvdb::GridPtrVecPtr const grids(stream.getGrids());

file.close();

uint32_t const grid_count(SFM::min(3, grids->size()));
for (uint32_t grid_index = 0; grid_index < grid_count; ++grid_index) {

GridType::Ptr const grid(openvdb::GridBase::grid((*grids)[grid_index]));

std::string const name(grid->getName()); // debug breakpoint here
}
```

Order of grid names needs to be the same when opened with openvdb::io::File or openvdb::io::Stream

The code above is a simple example needed to reproduce the problem and observe the resulting bug.