Use error dictionaries for community program components

We need to follow the project style guidelines for error handling and use shared error dictionaries instead of local component-based constants to avoid duplicates. See example here.

As a part of this, we should also use new Error(...), potentially with a cause, so the error handling is consistent with the rest of the application (example).

This issue covers components under ~/javascripts/subscription/components/community_program/.

More information in the original thread here: https://gitlab.com/gitlab-com/marketing/developer-relations/strategy-programs/open-source-program/gitlab-for-open-source/-/issues/51#note_2473519230