Current key handling strategy in TF-M

• Crypto keys are embedded at compile time and they are part of the secure image or bootloader.
• This behaviour is unlikely in a real device.
• It is expected that some mandatory crypto keys is provisioned to immutable memory at the factory floor.

The scope of the task is to simulate the real-life key provisioning with:

• Define a new flash area per target device to store keys there
• Create a binary object at compile time which contains the necessary crypto keys: HUK, attestation private key, image signing key(s).
• Update documentation how to load the key object to device memory.
• Modify platform example code to not contain any embedded crypto key instead retrieving the keys from dedicated flash area.