Top-level (arti and arti-client) features to enable crypto acceleration

These need to be optional: they improve performance by shifting to asm implementations, which may not be everybody's idea of good practice.

These are not 'pure' features, since they select one implementation but disable another. Therefore they don't go in full.

Closes #441 (closed).

assigned to @nickm

requested review from @eta

approved this merge request

lgtm! feel free to merge after resolving conflicts

added 25 commits

• 10b38a7d...0223c91b - 24 commits from branch tpo/core:main
• c4a9c8a1 - Merge branch 'main' into 'accel-features'

Compare with previous version

enabled an automatic merge when the pipeline for c4a9c8a1 succeeds

merged

mentioned in commit e1fc59ba