Support non-default mesh in serac driver

Currently we only support a single default mesh. Each physics module should be able to support different meshes via some input file functionality that doesn't exist atm.

Start by tracing the serac driver and how the current single default mesh is configured. Then inspect how physics modules receive mesh information and how input files are handled. Done means each physics module can select and use a different mesh through a defined input-file mechanism.

Written by the indexing model from the issue text.