Fixes DiscountCode errors type, adds new BatchResult type

[sle-c]

Description

Follow up on #1205

• What is the problem it is solving?
  DiscountCode has duplicated errors field which is only returned on batch operation results.

• What is the context of these changes?
  Adds new return type using BatchResult struct and new method to return the right type for batch result request in https://shopify.dev/docs/api/admin-rest/2024-01/resources/discountcode#get-price-rules-price-rule-id-batch-batch-id-discount-codes

• What is the impact of this PR?
  This adds a new method and deprecate an existing method. It should not impact existing users, and migration is optional.

How has this been tested?

Setup a new ruby project with the following script

# main.rb
require 'shopify_api'

access_token = '<truncated>'
shop = '<truncated>'

test_session = ShopifyAPI::Auth::Session.new(
  shop:,
  access_token:
)

ShopifyAPI::Context.setup(
  api_key: '<truncated>',
  api_secret_key: '<truncated>',
  api_version: '2024-01',
  scope: 'read_products, price_rules',
  is_private: false,
  is_embedded: true
)

ShopifyAPI::Context.activate_session(test_session)

response = ShopifyAPI::DiscountCode.get_batch_results(
  session: test_session,
  price_rule_id: 1445781537073,
  batch_id: 416335102257,
)
p response

Run it with

bundle exec ruby main.rb

This script prints the following result

[
  <ShopifyAPI::DiscountCode::BatchResult code="SUMMERSALE10OFF1" errors={"code"=>["must be unique. Please try a different code."]} id=nil>, 
  <ShopifyAPI::DiscountCode::BatchResult code="SUMMER2" errors={"code"=>["must be unique. Please try a different code."]} id=nil>, 
  <ShopifyAPI::DiscountCode::BatchResult code="SUMMER3" errors={"code"=>["must be unique. Please try a different code."]} id=nil>
]

Checklist:

• My commit message follow the pattern described in here
• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the project documentation.
• I have added a changelog line.

[sle-c]

closed because we decided that this issue is not worth fixing given that the documentation and generated will be diverged by this solution