[Uptime] Refactor header (#58836)

Cleanup implementation of the header to let pages embed the header rather than the weird sort of control the header works with today. Also uses kibana context in a way that makes more sense, and provide a path forward for #53550 since that will need to add a new header type (and some buttons next to the picker).

Fixes #58835

x-pack/legacy/plugins/uptime/public/breadcrumbs.ts

@@ -3,22 +3,3 @@
  * or more contributor license agreements. Licensed under the Elastic License;
  * you may not use this file except in compliance with the Elastic License.
  */
-
-import { i18n } from '@kbn/i18n';
-import { ChromeBreadcrumb } from 'src/core/public';
-
-const makeOverviewBreadcrumb = (search?: string): ChromeBreadcrumb => ({
-  text: i18n.translate('xpack.uptime.breadcrumbs.overviewBreadcrumbText', {
-    defaultMessage: 'Uptime',
-  }),
-  href: `#/${search ? search : ''}`,
-});
-
-export const getOverviewPageBreadcrumbs = (search?: string): ChromeBreadcrumb[] => [
-  makeOverviewBreadcrumb(search),
-];
-
-export const getMonitorPageBreadcrumb = (name: string, search?: string): ChromeBreadcrumb[] => [
-  makeOverviewBreadcrumb(search),
-  { text: name },
-];