feat(ContractContractService): update `get_fiber_contracts_to_pack` method

CHANGELOG:

### Added
- [#943](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/943) Exclude from method `get_fiber_contracts_to_pack` fiber contracts already referenced within mobile change tariffs or within new  mobile provisioning leads

Method get_fiber_contracts_to_pack now checks if any of the available (not packed) fiber contracts in Odoo is already referenced as contract to pack with in any ChangeTariffTickets (with bonified mobile products) in OTRS, or referenced as fiber related contract in any mobile lead line with pack product.

Related card: https://trello.com/c/idFy3X4G/1481-filtrar-de-lendpoint-de-fibres-lliures-les-que-estan-referenciades-en-tiquets-dotrs-per-canvis-de-tarifa-a-producte-bonificat

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⚠ Depends on: https://git.coopdevs.org/coopdevs/som-connexio/otrs-somconnexio/-/merge_requests/171 and https://git.coopdevs.org/coopdevs/som-connexio/otrs-somconnexio/-/merge_requests/175