Is your feature request related to a problem? Please describe.
Spawned from #404 discussion - osapi-os-core.h is a monolithic include covering a vast array of APIs, which makes changes harder conceptually separate and manage.

Describe the solution you'd like
Break up osapi-os-core.h - could use the deprecation process to avoid breakage where osapi-os-core.h just includes all the more focused headers.

Describe alternatives you've considered
None

Additional context
None

Requester Info
Jacob Hageman - NASA/GSFC