Blueprint Reader does the right thing for uniform coords + unstructured topos

[JustinPrivitera]

Description

Resolves #19057

Fix two bugs:

• handle the uniform coords + unstructured topo case
• prevent values leaf from being added to uniform coordsets by accident, causing 1D curves built off uniform coordsets to be unusable

Type of change

• [x] Bug fix~~
• ~~[ ] New feature~~
• ~~[ ] Documentation update~~
• ~~[ ] Other~~

How Has This Been Tested?

Reminders:

• Please follow the style guidelines of this project.
• Please perform a self-review of your code before submitting a PR and asking others to review it.
• Please assign reviewers (see VisIt's PR procedures for more information).

Checklist:

• [x] I have commented my code where applicable.~~
• [x] I have updated the release notes.~~
• ~~[ ] I have made corresponding changes to the documentation.~~
• ~~[ ] I have added debugging support to my changes.~~
• [x] I have added tests that prove my fix is effective or that my feature works.~~
• [x] I have confirmed new and existing unit tests pass locally with my changes.~~
• [x] I have added new baselines for any new tests to the repo.~~
• [x] I have NOT made any changes to protocol or public interfaces in an RC branch.~~