RESOLVES CORE-1204
**What**
- Fix wrong price tier when multiple items are targetting the same variant
- fix type import from the wrong package
**Notes**
If you are struggling navigating the changes, you can focus on the following files:
```
integration-tests/http/__tests__/cart/store/cart.spec.ts
integration-tests/modules/__tests__/cart/store/cart.workflows.spec.ts
packages/core/core-flows/src/cart/steps/get-promotion-codes-to-apply.ts
packages/core/core-flows/src/cart/steps/get-variant-price-sets.ts
packages/core/core-flows/src/cart/workflows/add-to-cart.ts
packages/core/core-flows/src/cart/workflows/create-carts.ts
packages/core/core-flows/src/cart/workflows/get-variants-and-items-with-prices.ts
packages/core/core-flows/src/cart/workflows/refresh-cart-items.ts
packages/core/core-flows/src/order/workflows/add-line-items.ts
packages/core/core-flows/src/order/workflows/create-order.ts
```