[TF-M] Example Partition Updates

Hi all,

Please be noted that the TF-M example Secure Partition has been moved from the tf-m-tools repo to the tf-m-extrashttps://git.trustedfirmware.org/TF-M/tf-m-extras.git/tree/examples/example_partition repo. It has also been aligned with the latest TF-M. The documentations are improved as well. It could be a good reference for Secure Partition developer starters.

Best Regards, Kevin