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-dir.h, function OS_DirectoryOpen():

• ONLY IN TEST: OS_FS_ERR_PATH_INVALID
• ONLY IN TEST: OS_FS_ERR_PATH_TOO_LONG
• OK: OS_INVALID_POINTER
• ONLY IN TEST: OS_SUCCESS

File src/os/inc/osapi-dir.h, function OS_DirectoryClose():

• ONLY IN TEST: OS_SUCCESS

File src/os/inc/osapi-dir.h, function OS_DirectoryRewind():

• ONLY IN TEST: OS_SUCCESS

File src/os/inc/osapi-dir.h, function OS_DirectoryRead():

• ONLY IN TEST: OS_ERR_INVALID_ID
• OK: OS_INVALID_POINTER

File src/os/inc/osapi-dir.h, function OS_mkdir():

• ONLY IN DOXY: OS_ERROR
• OK: OS_FS_ERR_PATH_INVALID
• OK: OS_FS_ERR_PATH_TOO_LONG
• OK: OS_INVALID_POINTER
• ONLY IN DOXY: OS_SUCCESS

File src/os/inc/osapi-dir.h, function OS_rmdir():

• OK: OS_ERROR
• OK: OS_FS_ERR_PATH_INVALID
• OK: OS_FS_ERR_PATH_TOO_LONG
• OK: OS_INVALID_POINTER
• OK: OS_SUCCESS

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

Requester Info
Joseph Hickey, Vantage Systems, Inc.