NEML2 kernels and tutorials

[zaheen1258]

PFFSource: Non AD source kernel. Brings the jacobian contribution from the propagated neml2 derivatives
mode1_brittle_fracture_neml2: mode1 using neml2 material models (covers decomposition: none and power degradation)
mixed_mode_Winklers_LBeam_neml2: mixed mode case using neml2 models (covers decomposition: voldev and rational degradation)

[hugary1995]

I removed the mode II and L beam tutorials to reduce some maintenance burden. We only need one tutorial to demonstrate the use of neml2. I changed the parameter names in PFFSource to stay consistent with ADPFFSource.

[zaheen1258]

I removed the mode II and L beam tutorials to reduce some maintenance burden. We only need one tutorial to demonstrate the use of neml2. I changed the parameter names in PFFSource to stay consistent with ADPFFSource.

Sounds Great!