Merge changes from topic "fwu-on-stm32mp1" into integration

* changes:
  feat(stm32mp1): add support for building the FWU feature
  feat(stm32mp1): add logic to pass the boot index to the Update Agent
  feat(stm32mp1): add support for reading the metadata partition
  feat(stm32mp1): add logic to select the images to be booted
  feat(stm32mp1): add GUID's for identifying firmware images to be booted
  feat(stm32mp1): add GUID values for updatable images
  feat(fwu): add platform hook for getting the boot index
  feat(fwu): simplify the assert to check for fwu init
  feat(fwu): add a function to pass metadata structure to platforms
  feat(partition): add a function to identify a partition by GUID
  feat(partition): copy the partition GUID into the partition structure
  feat(partition): make provision to store partition GUID value
  feat(partition): cleanup partition and gpt headers
  feat(fwu): add basic definitions for GUID handling
  feat(fwu): pass a const metadata structure to platform routines
  build(changelog): add a valid scope for partition code