Migrate page breadcrumbs to BreadcrumbList

Migrate $0 (a file, a view directory, or the next unmigrated call site when omitted) off sentry/components/breadcrumbs.

The transformation

Legacy passes one flat array in which the last crumb is the current page (the component strips its to automatically). The new API splits that across two TopBar slots.

// Old — one array, leaf included
<Breadcrumbs crumbs={[{label: t('Monitors'), to: basePath}, {label: monitor.name}]} />