[elasticsearch-plugin] Optimize priceRange method

[Izayda]

Is your feature request related to a problem? Please describe.
Now, when we query prices field in search query we always trigger rather heavy query despite of attributes listed in prices field.

For example, if we want to get only

range {
    min
    max
}

we don't need to send to elastic whole query

Describe the solution you'd like
Elastic plugin dynamically determine what aggregations should be send to elastic instance.

Describe alternatives you've considered
Just be slightly slower.

[michaelbromley]

Yes, that's true. The advanced search plugin is already doing this kind of optimization, which is achieved by introspecting the GraphQL query like this:

async search(ctx: RequestContext, args: QuerySearchArgs, info: GraphQLResolveInfo) {
        const selectedFields = this.getSearchSelectedFieldNames(info);
        return this.searchService.search(ctx, selectedFields, args.input || undefined);
    }

    protected getSearchSelectedFieldNames(info: GraphQLResolveInfo): Array<keyof SearchResponse> {
        function getFieldNodes(selectionSet: SelectionSetNode): FieldNode[] {
            const fields: FieldNode[] = [];
            for (const selectionNode of selectionSet.selections) {
                switch (selectionNode.kind) {
                    case 'Field':
                        fields.push(selectionNode);
                        break;
                    case 'FragmentSpread':
                        const fragment = info.fragments[selectionNode.name.value];
                        if (fragment) {
                            fields.push(...getFieldNodes(fragment.selectionSet));
                        }
                        break;
                    case 'InlineFragment':
                        fields.push(...getFieldNodes(selectionNode.selectionSet));
                        break;
                    default:
                        assertNever(selectionNode);
                }
            }
            return fields;
        }

        const searchField = info.fieldNodes.find((node) => node.name.value === 'search');
        if (searchField && searchField.selectionSet) {
            const fields = getFieldNodes(searchField.selectionSet);
            return fields.map((f) => f.name.value as keyof SearchResponse);
        }
        return [];
    }