introduce annotation #[stable_call_conv]

[bgregoir]

Description

Please include a summary of the changes and the related issue (if applicable). Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes # (issue)

Checklist

• [] Add a changelog entry in changes if the PR is a user-visible change
• [x] Add one or several tests to compiler/tests if it makes sense, especially if it is a bug fix
• [x] Update the documentation if needed