mgr/dashboard: Use custom classes for form label and inputs

mgr/dashboard: Use custom classes for form label and inputs

With this change we are able to configura the col sizes of labels and inputs in
one single place.

Also increased the col size in smaller screens to be able to display longer
labels.

This was not applied in some situations where the col size was different than
usual.

Fixes: https://tracker.ceph.com/issues/40751
Signed-off-by: Tiago Melo <tmelo@suse.com>