Is your feature request related to a problem? Please describe.
The unit tests and API documentation should match, where all status codes in the API documentation are tested in a unit test, and likewise all codes being tested for are documented in the API.

Describe the solution you'd like
Resolve the following mismatches:

File src/os/inc/osapi-heap.h, function OS_HeapGetInfo():

• ONLY IN DOXY: OS_INVALID_POINTER

File src/os/inc/osapi-network.h, function OS_NetworkGetHostName():

• OK: OS_ERR_INVALID_SIZE
• OK: OS_INVALID_POINTER
• ONLY IN TEST: OS_SUCCESS

File src/os/inc/osapi-shell.h, function OS_ShellOutputToFile():

• ONLY IN DOXY: OS_ERROR
• OK: OS_ERR_INVALID_ID
• OK: OS_INVALID_POINTER
• ONLY IN DOXY: OS_SUCCESS

Additional context
Originally noted in #331, split into separate work items.

Requester Info
Joseph Hickey, Vantage Systems, Inc.