Update PSP library to work with CMake interface logic

[jphickey]

Is your feature request related to a problem? Please describe.
PSP should "publish" its public API interface via CMake using target_include_directories and target_compile_definitions such that other modules that link to PSP (e.g. CFE core) will automagically get the include dirs and definitions without having to hard-code them.

Describe the solution you'd like
Use "target_include_directories" and "target_compile_definitions" to advertise the interface

Additional context
Required for moving toward an interface-based build.

Requester Info
Joseph Hickey, Vantage Systems, Inc.