[Feature] [API] get/post/delete issue/pull/comment attachments

[6543]

as it is posible with release attachments

[stale]

This issue has been automatically marked as stale because it has not had recent activity. I am here to help clear issues left open even if solved or waiting for more insight. This issue will be closed if no further activity occurs during the next 2 weeks. If the issue is still valid just add a comment to keep it alive. Thank you for your contributions.

[andrebruch]

I have added the feature for issues and comments in #14601.

[6543]

dublicate of #3690