[Fix] vit_operators

• Compute axis values in computeOutputDims() instead of forward kernel

changed milestone to %aidge_core - v0.2.0

assigned to @pineapple

changed target branch from main to dev

added 20 commits

• 8b401c1f...f0917214 - 18 commits from branch dev
• e341bc78 - [WIP][NF] update ReduceMean
• e941e9fe - [Fix] set axis conversion to positive values in 'computeOutputDims()'

Compare with previous version

enabled an automatic merge when the pipeline for e941e9fe succeeds

mentioned in commit 95077929

merged