Remove legacy `twig/twig` version conflicts that blocked users of
standalone bundles from upgrading to Twig 3.x:

- Remove `^3.0` conflict added in 2019, already removed in Sylius 2.0+
- Remove `^1.0` conflict (Twig 1.x reached EOL years ago)
- Keep `3.9.0` conflict as it's a specific buggy version documented in
`CONFLICTS.md`

Since Twig 2.x reached EOL in December 2023, these conflicts were
blocking users who use Sylius bundles standalone from upgrading.

Also adds `friendsofsymfony/rest-bundle` and `jms/serializer-bundle` to
UserBundle `require-dev` - they're used in functional tests but were
previously installed as transitive dependencies of
`sylius/resource-bundle` (moved from `require` to `require-dev` in
ResourceBundle 1.13).

Additionally adds conflict for `liip/imagine-bundle: 2.17.0` - this
version was released on 2026-01-05 and breaks container compilation when
AssetMapper is not used (unrelated to twig changes).

Affected bundles: AddressingBundle, CustomerBundle, CurrencyBundle,
InventoryBundle, LocaleBundle, MoneyBundle, OrderBundle, PaymentBundle,
PromotionBundle, ReviewBundle, ShippingBundle, TaxationBundle,
TaxonomyBundle, UiBundle, UserBundle

Closes #18700