Use a consistent commit from consuming branches

[gilles-peskine-arm]

There is a race condition on the CI for https://github.com/Mbed-TLS/mbedtls-framework and https://github.com/Mbed-TLS/TF-PSA-Crypto. They perform some testing with consuming branches from https://github.com/Mbed-TLS/mbedtls. It uses the head of the consuming branch. If the consuming branch moves during the execution of the script, different parts of the job may test against different commits. This can result in spurious failures (or potentially spurious passes, but I don't think that's likely).

Example: in a merge queue job on TF-PSA-Crypto, most of the CI run used the mbedtls development branch at eb20c1f12d54aefba8a22c293721900b1d63a1cb, but the result-analysis job used a more recent commit 50432e42c88991743d4b4a9bb732d5313fe026e8. The more recent commit had additional test cases, and those test cases were never executed (because they weren't merged yet when the all.sh components ran), but they were picked up by result analysis since they had been merged by that time.