perf: reduce cppcore initialisation

[ilkilic]

Description

Reduces redundant dependency tree initialisations in cppcore, improving feature extraction performance by up to 2.5x. The change ensures getFeatureValues avoids unnecessary resets, with efel.reset available for reloading dependencies when needed.

Checklist:

• Unit tests are added to cover the changes (skip if not applicable).
• The changes are mentioned in the documentation (skip if not applicable).
• CHANGELOG file is updated (skip if not applicable).

[AurelienJaquier]

nice!