MultiWriter: extend AdiosReplay to handle multiple simulation as input

Context

In some scenario, a whole simulation can be composed of a subset of simulation which handle different usage.

In this case, we may want to be able to visualize the whole simulation which is not supported for now as the implementation can only take a single simulation in input.

Solutions

The solution proposed is to allow the user define a catalyst adaptor for each of theses simulations.
The custom catalyst2 implementation AdiosCatalyst will create an Adios2 context for each of them.
Then, the AdiosReplay will be responsible for aggregating each entry into a single conduit node for the ParaViewCatalyst implementation as described in the following schema:

Schema

Technical part

• A new example Example/MultipleWriter should be added with a dedicated README.md about how to test it.
• To be able to retrieve multiple Adios2 context we need to improve the support of gs.bp file generated by each Adios2 context. For that, each catalyst_adaptor will require an additional meta information named sstFileName. It will fix this issue #4 (closed)
• For the aggregation, AdiosReplay should be refactored to handle multiple simulation
• The outputed conduit node will need to support different use case:
  • the outputed conduit node should be a multimesh if there is several inputs
  • a multimesh can't contains a multimesh so we need to flatten it.