Move tests/scripts/check-generated-files.sh to the framework

[mpg]

This script has diverged between development and 3.6. This task is to:

• reconcile the two branches;
• move the script to the framework;
• adapt the path everywhere the script is invoked.

Note: this task is only about mbedtls and the framework. This script is supposed to be already adapted to tf-psa-crypto; we just need to take care not to undo that while reconciling the two mbedtls branches - this will likely mean aligning on the development version in most cases, but please consider for each case if that is indeed the right thing to do.

[gilles-peskine-arm]

Should we move it to the framework, or should we do without it? Related discussion: Mbed-TLS/TF-PSA-Crypto#50 (comment)

[gilles-peskine-arm]

adapt the path everywhere the script is invoked.

Note that this may include references outside the mbedtls repository. I'm aware of the following:

• The new Coverity push script from Add coverity push script mbedtls-test#165 relies on check-generated-files.sh -u.
• https://github.com/Mbed-TLS/mbedtls-docs/blob/main/kb/how-to/add-test-generation.md references check-generated-files.sh.