authz: add `TouchRepoPermissions` API
Created by: unknwon
Quoting from docstring:
// TouchRepoPermissions only updates the value of both `updated_at` and `synced_at` columns of the
// `repo_permissions` table without modifying the permissions bits. It inserts a new row when the
// row does not yet exist. The use case is to trick the scheduler to skip the repository for syncing
// permissions when we can't sync permissions for the repository (e.g. due to insufficient permissions
// of the access token).
Easier to review by commit.
Tested end-to-end.
Fixes #14701