Existing GSG violations: non-trivially destructible types at a static storage duration?

## Environment
N/A

## Description
* Expected behavior: All static storage duration stuff (`static`, global `const`, etc.) should be trivially destructible per GSG
* https://ignitionrobotics.org/docs/all/contributing#style-guides
* https://google.github.io/styleguide/cppguide.html#Static_and_Global_Variables
* Actual behavior: It's still a tad mixed atm:

https://github.com/osrf/sdformat/blob/689ee8410a97917e2087ffd5045861d63258ebd4/include/sdf/Types.hh#L64-L72

## Steps to reproduce
N/A

## Output
N/A

Start with include/sdf/Types.hh at lines 64-72, then audit the repository for other static-storage-duration declarations covered by the linked GSG guidance. Confirm which types are non-trivially destructible and define completion as bringing the identified declarations into compliance without changing their intended behavior. No specific test file is mentioned, so run the existing validation suite after the audit.

Written by the indexing model from the issue text.