mgr/dashboard: Landing Page improvements

mgr/dashboard: Landing Page improvements

Fixes: https://tracker.ceph.com/issues/42072
Signed-off-by: Alfonso Martínez <almartin@redhat.com>
(cherry picked from commit d66e684b9ec83cca8a58b0a7b8661c568eb0cf6d)

 Conflicts:
	src/pybind/mgr/dashboard/frontend/src/app/ceph/dashboard/health-pie/health-pie.component.scss
	src/pybind/mgr/dashboard/frontend/src/app/ceph/dashboard/health/health.component.html
	src/pybind/mgr/dashboard/frontend/src/app/ceph/dashboard/health/health.component.ts
	src/pybind/mgr/dashboard/frontend/src/app/ceph/dashboard/info-card/info-card.component.scss
	src/pybind/mgr/dashboard/frontend/src/styles/defaults/_bootstrap-defaults.scss
	  this file doesn't exist in octopus, so I moved the code into:
	src/pybind/mgr/dashboard/frontend/src/stykes/defaults.scss