Map Selected Custom Options to GQL shema

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Source: https://github.com/magento/catalog-storefront/issues/172
TODO: add a description

**Changes to proto schema to align it with GraphQL schema needs:**

GraphQL => proto Mapping:

```
interface CustomizableProductInterface {
options: [CustomizableOptionInterface] // map to Product::options
}

interface CustomizableOptionInterface { // ProductOption
option_id: // ProductOption::id
title: // ProductOption::label
required: // ProductOption::required
sort_order: // ProductOption::sort_order
}

type CustomizableRadioOption implements CustomizableOptionInterface { //ProductOption
value: [CustomizableRadioValue] // ProductOptionValue
}

type CustomizableRadioValue { //ProductOptionValue
option_type_id: // deprecated
uid: // ProductOptionValue::id
price: // ProductVariant::product_identifier_in_pricing
price_type: // deprecated. We would always have precalculated price for variant.
sku: // deprecated. Doesn't use on UI
title: // ProductOptionValue::label
sort_order: // ProductOptionValue::sort_order
}

type CustomizableDropDownOption implements CustomizableOptionInterface { //ProductOption
value: [CustomizableDropDownValue] //ProductOptionValue
required: // ProductOption::required
}

type CustomizableDropDownValue { //ProductOptionValue
option_type_id: // deprecated
uid: // ProductOptionValue::id
price: // ProductVariant::price
price_type: // deprecated. We would always have precalculated price for variant.
sku: // deprecated. Doesn't use on UI
title: // ProductOptionValue::label
sort_order: // ProductOptionValue::sort_order
}

```

Start with the linked catalog-storefront issue 172 and the GraphQL-to-proto mapping in this issue. Identify where the product option schema is defined and how selected custom options are represented. Done means the proto schema aligns with the listed GraphQL option and value fields, including deprecated fields and pre-calculated pricing behavior.

Written by the indexing model from the issue text.