Allow option to multi select repositories while applying permissions at project settings

Currently if users apply permissions such as default reviewers or branch permissions under project settings, these permissions are by default inherited by all the repositories and they cannot be removed for a specific repository. Providing an option to multi select repository would help in resolving this issue.

Use case: If Admins want new set of users( default reviewers) to be added for a specific repo they cannot make changes to inherited list.