Compute effective inelastic strain

[dschwen]

Reason

Effective inelastic strain is a useful measure for the plastic deformation of a material. We should also use its increment to compute the material timestep. The value is very likely already computed by NEML (@reverendbedford ?), but we currently have no reliable way of obtaining it (if it is in the history). That's a separate issue (i.e. getting the history index for a specific quantity).

Design

Compute inelastic strain increment, from there compute effective inelastic strain increment, and using a scalar stateful property, integrate this to effective inelastic strain.

Possibly only do that on non-linear iterations (i.e. currentlyComputingJacopian() == true)

Impact

Added capability