Catalyst: Need support for optionally creating meshes and/or variables in Conduit
Currently, every time Catalyst is called, it is expected that the simulation populates the Conduit data structures for ParaView to consume. This means that even if there are extractors with frequencies > 1 per time step, data is being converted every time, which may be costly. Even though it is possible to manage the frequency on the simulation side, this reduces the usefulness of having a frequency parameter for the extractors. Furthermore, different pipelines/extractors may need different meshes and/or variables and the current implementation is all or nothing because ParaView has no means to communicate what it needs to the simulation adaptor populating the Conduit tree.