mgr/dashboard: Switch ng2-toastr for ngx-toastr

mgr/dashboard: Switch ng2-toastr for ngx-toastr

Fixes: https://tracker.ceph.com/issues/40768
Signed-off-by: Tiago Melo <tmelo@suse.com>
(cherry picked from commit 67f5e5b18b71ccabcaa8d9e35c57630d17395b06)
Signed-off-by: Ernesto Puerta <epuertat@redhat.com>
Required manual (trivial) fixing of the following files:
Conflicts:
      src/pybind/mgr/dashboard/frontend/package.json
      src/pybind/mgr/dashboard/frontend/src/app/ceph/cluster/prometheus/alert-list/alert-list.component.spec.ts
      src/pybind/mgr/dashboard/frontend/src/app/ceph/cluster/prometheus/silence-form/silence-form.component.spec.ts
      src/pybind/mgr/dashboard/frontend/src/app/ceph/cluster/prometheus/silence-list/silence-list.component.spec.ts
      src/pybind/mgr/dashboard/frontend/src/app/ceph/pool/pool-list/pool-list.component.spec.ts
      src/pybind/mgr/dashboard/frontend/src/app/shared/services/prometheus-notification.service.spec.ts