[hardware] :bug: Fix reductions + Rework the VALU

[mp-17]

The previous mechanism to handle the commit during a reduction was confusing and led to bugs. Now, the reduction triggers its commit only after the inter-lanes phase is over. Also, some recurrent lines of code have been grouped into macros

Changelog

Fixed

• Description of changes

Added

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Changed

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Checklist

• [x] Automated tests pass
• [x] Changelog updated
• [x] Code style guideline is observed
• [ ] No frequency degradation