Migrate page breadcrumbs to BreadcrumbList

Migrate the requested file or view directory. If no target is supplied, inspect the remaining legacy importers and select a page-navigation call site.

The transformation

Separate parent links from the current page title. Pass both through one public slot:

// Legacy: one array, including the current page.
<Breadcrumbs crumbs={[{label: t('Monitors'), to: basePath}, {label: monitor.name}]} />

// Current: required typed title, optional parent breadcrumbs.
<TopBar.Slot
  name="breadcrumbs"
  title={{type: 'page-title', label: monitor.name}}
  items={[{type: 'link', label: t('Monitors'), to: basePath}]}
/>