mgr/dashboard: Refresh button on the iscsi targets page

mgr/dashboard: Refresh button on the iscsi targets page

Added a refresh button on the iscsi targets page. I've noticed that the
auto reload causes some load on the backend. So I disabled the auto
reload and went for the same approach as we have on rgw. A yellow
warning color on refresh btn to let the user know to manually refresh
that whenever needed.

Fixes: https://tracker.ceph.com/issues/52102
Signed-off-by: Nizamudeen A <nia@redhat.com>
(cherry picked from commit 8f23a587a8ccc686b1e3acbfa587fcab76bee45d)