Add GraphQL/REST info for uploading files to ACCS

[keharper]

This reverts commit 9c630cc.

Purpose of this pull request

This pull request introduces comprehensive documentation updates to support and explain new SaaS-only file and image upload features in Adobe Commerce's GraphQL API, particularly focusing on Amazon S3 integration for custom attributes and B2B negotiable quotes. It also enhances navigation for these new features and provides detailed usage examples for both REST and GraphQL APIs.

GraphQL SaaS file/image upload and S3 integration:

• Added documentation and usage examples for retrieving presigned S3 URLs for customer-uploaded files and images via new AttributeFile and AttributeImage implementations of AttributeValueInterface (SaaS only), including backward compatibility notes for migrations.
• Provided detailed step-by-step GraphQL examples for uploading files to S3, referencing them in customer addresses, and retrieving them, including new mutation and query samples.

B2B negotiable quote attachments:

• Updated negotiable quote mutation and query examples to demonstrate attaching and retrieving files via S3, including new fields in the schema, example requests/responses, and SaaS edition callouts.

Navigation and structure improvements:

• Added new navigation sections for GraphQL and REST documentation to surface S3 upload capabilities and related mutations.

General enhancements and clarifications:

• Added edition callouts and inline alerts to clarify SaaS-only features and highlight backward-incompatible changes for users migrating from on-premise or cloud infrastructure.