PINN variants addition and Solvers Update (#263)

* gpinn/basepinn new classes, pinn restructure
* codacy fix gpinn/basepinn/pinn
* inverse problem fix
* Causal PINN (#267)
* fix GPU training in inverse problem (#283)
* Create a `compute_residual` attribute for `PINNInterface`
* Modify dataloading in solvers (#286)
* Modify PINNInterface by removing _loss_phys, _loss_data
* Adding in PINNInterface a variable to track the current condition during training
* Modify GPINN,PINN,CausalPINN to match changes in PINNInterface
* Competitive Pinn Addition (#288)
* fixing after rebase/ fix loss
* fixing final issues

---------

Co-authored-by: Dario Coscia <dariocoscia@Dario-Coscia.local>

* Modify min max formulation to max min for paper consistency
* Adding SAPINN solver (#291)
* rom solver
* fix import

---------

Co-authored-by: Dario Coscia <dariocoscia@Dario-Coscia.local>
Co-authored-by: Anna Ivagnes <75523024+annaivagnes@users.noreply.github.com>
Co-authored-by: valc89 <103250118+valc89@users.noreply.github.com>
Co-authored-by: Monthly Tag bot <mtbot@noreply.github.com>
Co-authored-by: Nicola Demo <demo.nicola@gmail.com>

docs/source/_rst/_code.rst

@@ -35,8 +35,14 @@ Solvers
     :titlesonly:
     
     SolverInterface <solvers/solver_interface.rst>
+    PINNInterface <solvers/basepinn.rst>
     PINN <solvers/pinn.rst>
+    GPINN <solvers/gpinn.rst>
+    CausalPINN <solvers/causalpinn.rst>
+    CompetitivePINN <solvers/competitivepinn.rst>
+    SAPINN <solvers/sapinn.rst>
     Supervised solver <solvers/supervised.rst>
+    ReducedOrderModelSolver <solvers/rom.rst>
     GAROM <solvers/garom.rst>