chart: add defaultNodeSelector for all components

Until now all the components that were not a daemonset and needed to be
deployed on a node contained a config option to indicate a node selector
for the allocation. This commits adds a new global option that allows to
set a node selector that will be applied to all the components that do
not declare one. If any component declares a node selector this last one
will have always more priority.

JIRA Refs:
- MONIT-4003