[Backport 3.6] Refactor all.sh

[mpg]

Description

This is the 3.6 backport of #9657.

The commits structure is as follows:

1. First, fully align all.sh with development:
   • mostly changes that had been done in development but not backported because they were useless there -> still add them because they're harmless;
   • one change that's not correct for 3.6 and will be revert in step 3 below.
2. Then cherry-pick commits from the development PR.
3. Then additional commits for 3.6:
   • Revert the change made at step 1 above that was incorrect.
   • Adapt some code to the absence of tf-psa-crypto in 3.6.

The two additional commits in step 3 have been forward-ported to the development PR, so at the end of these PRs, all-core.sh and all-helpers.sh should be identical between branches.

PR checklist

Please remove the segment/s on either side of the | symbol as appropriate, and add any relevant link/s to the end of the line. If the provided content is part of the present PR remove the # symbol.

• [x] changelog not required because: internal, tests only
• [x] development PR provided #9657
• [x] framework PR not required
• [x] 3.6 PR here
• [x] 2.28 PR not required because: not worth it (also, we already didn't split components-*.sh out of all.sh there).
• tests not required because: covered by existing tests