Refactor: Change instances of override to optin in dpm repo

With the sunsetting of overriding components with 3.5, we should replace references of overrides with optin to improve code readability

Search the dpm repository for references to “override” and related forms, then review each occurrence in context before replacing the terminology with “optin.” Confirm the repository no longer contains the outdated references and run the available checks to ensure the refactor does not break the package manager.

Written by the indexing model from the issue text.