Keep DataAccess namespace param in sync with the workspace's datastore until the resource/publish split is complete

We're allowing to change the workspace AND the dataaccess namespace parameter independently, but it leads to issues since the resource/publish split is not really finished yet. So since we need to rely on the assumption of namespace being the same than the one linked to the workspace, do not allow to edit the datastore namespace, make it read only and auto update it whenever the datastore's workspace is changed. This can be easily reverted when the split is done.