[WIP] Take ownership of `Param`s

[BenWibking]

PR Summary

When Params are created or updated, it takes ownership of the object passed with std::move.

PR Checklist

• [ ] Code passes cpplint
• [ ] New features are documented.
• [ ] Adds a test for any bugs fixed. Adds tests for new features.
• [ ] Code is formatted
• [ ] Changes are summarized in CHANGELOG.md
• [x] 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)
• [ ] CI has been triggered on Darwin for performance regression tests.
• [ ] Docs build
• [ ] (@lanl.gov employees) Update copyright on changed files

[BenWibking]

@Yurlungur is there a reason for a custom Params container? Could this be replaced with a wrapper around a std::unordered_map<std::string, std::any>?

Although I see that std::any only works for copy-constructible objects...

[Yurlungur]

Thanks for taking a stab at this!

@Yurlungur is there a reason for a custom Params container? Could this be replaced with a wrapper around a std::unordered_map<std::string, std::any>?

We wrote Params when Parthenon was C++14 only. So at the time it wasn't an option. In principle, I think it could be replaced with std::any modulo the issue with copy constructible types.

I am somewhat concerned also about how this will interact with I/O. In principle it should all work though.