How to give an 'editor' role rebuild/clear cache permission?
To access this, they would need the administer site configuration permission.

From system.routing.yml:

system.performance_settings:
  path: '/admin/config/development/performance'
  defaults:
    _form: 'Drupal\system\Form\PerformanceForm'
    _title: 'Performance'
  requirements:
    _permission: 'administer site configuration'