Adapt Change holder wizard to packs flow

CHANGELOG:

### Changed
- [#944](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/944) Adapt Change holder wizard to packs flow

Related card: https://trello.com/c/5lCNZTkj/1478-modificacions-al-wizard-canvi-de-titular

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• Show in the wizard if mobile pack offer is available.
• Selector with the product to choose.