Add "psp_module_api" interface target

[jphickey]

Is your feature request related to a problem? Please describe.
PSP should provide and use an interface library target for all of its own modules. This simplifies the build.

Describe the solution you'd like
Add a psp_module_api interface library target to go along with the core_api interface target being added in nasa/cFE#1203.
Fix remaining uses of directory-scope properties and change to target properties.

Additional context
Continuation of #254/#255 - where #255 just made PSP work with CFE after CFE transitioned to interface libraries, this makes PSP also use interface libraries internally and for all its components.

Requester Info
Joseph Hickey, Vantage Systems, Inc.