Add example program for PSA sign verify

[tom-daubney-arm]

Description

This PR contains the PSA sign verify program, originally authored by @hannestschofenig .

This PR is the seventh part of a series of PRs that are based on https://github.com/Mbed-TLS/mbedtls/pull/5064 , which has been split in order to make reviewing easier.

PR checklist

Please tick as appropriate and edit the reasons (e.g.: "backport: not needed because this is a new feature")

• changelog done
• backport not required
• tests not required

Notes for the submitter

Please refer to the contributing guidelines, especially the checklist for PR contributors.

[daverodgman]

Test comment

[tom-daubney-arm]

Note for reviewers: I think I have implemented all of the general feedback that came from #7942 in to this program, where relevant. As such, I have removed the needs-design-approval label and marked ready for review.