IC:2021-09-07, cFE, osal, psp, sch_lab

**Combines**

nasa/cFE#1939, v6.8.0-rc1+dev994
nasa/osal#1145, v5.1.0-rc1+dev604
nasa/PSP#307, v1.5.0-rc1+dev124
nasa/sch_lab#87, v2.4.0-rc1+dev47

**Includes**

*cFE*

nasa/cFE#1903, Update directory diagrams in application developer guide

nasa/cFE#1922, SB code coverage improvements #1905, Improve SB coverage

nasa/cFE#1936, Improve ES code coverage

nasa/cFE#1938, Enforce minimum code coverage

nasa/cFE#1940, Update dev guide for MSG and SBR

nasa/cFE#1941, Support unimplemented features in MSG FT

*osal*

nasa/osal#1144, Regex update in coverage enforcement to match .0

nasa/osal#1142, Add typecast to memchr call

*psp*

nasa/PSP#307, check that module type is not invalid

nasa/PSP#306, do not override add_psp_module for coverage test

*sch_lab*

nasa/sch_lab#86, add CmdCode to sch_lab_table

nasa/sch_lab#88, Fix missing typedef

Co-authored-by: Jacob Hageman           <[email protected]>
Co-authored-by: Joseph Hickey           <[email protected]>
Co-authored-by: Ariel Adams             <[email protected]>
Co-authored-by: Jose F Martinez Pedraza <[email protected]>