Uobjcoll-arm-trusted-firmware: fixes and tests with native and uobjcoll builds

This task will test the native build on the STM32MP1 board and incorporate related fixes to both native and uobjcoll build harness

PRs:

Merges:

Tested native build and execution on STM32MP1 development board. Also tested uobjcoll build with success. Added documentation and build-harness fixes in the process. Changes merged upstream. Linked PR and merge info to OP. Closing topic thread.