Enhance bevymark (#9674)

# Objective

- In preparation for an initial 2D/3D mesh batching/instancing PR,
enhance `bevymark` to support some different test modes that enable
comparison and optimisation of performance
 
## Solution

- Use `argh` for command line interface options
- Use seeded `StdRng` for reproducible random number generation
- Add a mode for testing 2D meshes that includes an option to uniquely
vary the data of each material by setting a random flat colour on the
`ColorMaterial`.
- Add a way of specifying the number of different textures to use for
sprites or meshes. These are generated at the same resolution as the
Bevy bird icon, but are just random flat colours for testing.
- Add a benchmark mode that spawns all entities during setup, and
animates the entities using a fixed delta time for reproducible
animation. The initially-spawned entities are still spawned in waves and
animated as they would have been had they spawned at intervals.

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Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>