Add EnzymeRules overloads

[ChrisRackauckas]

Similar to https://github.com/SciML/LinearSolve.jl/blob/main/ext/LinearSolveEnzymeExt.jl, NonlinearSolveBase.jl should add EnzymeRules overloads over the nonlinear solver for the implicit adjoint.

[jClugstor]

Isn't that what the current EnzymeExt does https://github.com/SciML/NonlinearSolve.jl/blob/master/lib/NonlinearSolveBase/ext/NonlinearSolveBaseEnzymeExt.jl ?

That goes through SciMLSensitivity and does SteadyStateAdjoint, right?

Or is this about implementing a forward rule?

[ChrisRackauckas]

yes this is covered.