Updates to `DataCollection`

[lroberts36]

PR Summary

This PR makes some changes to DataCollection so that calling pmesh->mesh_data.GetOrAdd(some_label, partition) works whether or not some_label has been previously added to the MeshBlockData container. Additionally, it makes it so that Add will now work correctly for MeshData (previously it didn't use the correct labeling and containers could be overwritten).

Possible other things to do:

• Formalize partitioning and move it to Mesh
• Get all of the DataCollection interface to work with both Mesh and MeshData
• Remove Initialize methods and replace them with constructors since they break RAII

PR Checklist

• [x] #991 is merged
• [x] Code passes cpplint
• [ ] New features are documented.
• [ ] Adds a test for any bugs fixed. Adds tests for new features.
• [x] Code is formatted
• [x] Changes are summarized in CHANGELOG.md
• [ ] Change is breaking (API, behavior, ...)
  • [ ] Change is additionally added to CHANGELOG.md in the breaking section
  • [ ] PR is marked as breaking
  • [ ] Short summary API changes at the top of the PR (plus optionally with an automated update/fix script)
• [x] CI has been triggered on Darwin for performance regression tests.
• [ ] Docs build
• [ ] (@lanl.gov employees) Update copyright on changed files

[pdmullen]

w.r.t. swarms, I tested this downstream and all looks good. I noticed that this PR is targeting lroberts36/add-fine-variables instead of develop... intentional?

[lroberts36]

I noticed that this PR is targeting lroberts36/add-fine-variables instead of develop... intentional?

@pdmullen: yeah, but only because I was using the new test I added there to check that removing the MeshBlockData boiler plate worked.

[Yurlungur]

@lroberts36 are we waiting for someone to review this?

[lroberts36]

@lroberts36 are we waiting for someone to review this?

@Yurlungur: @pgrete said he would on Thursday, but I think he has been under the weather the last few days.

[lroberts36]

"Remove Initialize methods and replace them with constructors since they break RAII" is possibly meant for a future PR, isn't it? In that case -> new issue?

@pgrete: I think I was just annoyed when I wrote this comment. It is probably not worth the effort to remove the initialization methods and replace them with constructors.