load mesh objects from weight_windows.h5 file

[GuySten]

Description

Currently, when openmc load weight windows from an hdf5 file the meshes are not loaded.
This PR change this behavior so the meshes inside the weight windows hdf5 file are also loaded.

Fixes #3588

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)

[pshriwise]

Thanks for this, @GuySten. One comment on separating concerns. We'll also want to attempt some testing for this of course if you're up for taking a crack at that.

[GuySten]

I've added tests for reading and writing mesh objects from HDF5.

[pshriwise]

Relatively minor things to address here and then I think this is good! I refactored the object generation code because it was duplicated between the two read_meshes versions and if we ever update that I'd like it to be able to be changed in one place.

Thanks for adding to the C++ tests! I really like seeing that suite grow. I also added a test for a roundtrip of multiple meshes that I think should pass once one of the comments is addressed.

[pshriwise]

Suggested change

	fatal_error("Number of entries on <lower_left> must be the same "
	"as the number of entries on <dimension>.");
	fatal_error("Number of entries on lower_left dataset must be the same "
	"as the number of entries for the mesh dimension.");

[pshriwise]

There are other, similar error messages that imply the mesh is read from an XML file that we should probably update below.

[pshriwise]

Alternatively, we could factor out some of this logical checking into new methods for RegularMesh and RectilinearMesh like the CylindricalMesh::set_grid method does.

[GuySten]

I decided to refactor most of the logical checking.

[pshriwise]

Thanks for this added capability @GuySten! I'll merge once tests are green.

@yrrepy maybe try this out and let us know how it goes?

[yrrepy]

Haven't given it a full shakedown, but it appears to do the task.