Add Vloop boundary condition for the psi equation

Vloop (= dpsi_edge/dt) can be a useful BC for scenarios where the voltage swing of the central solenoid is directly controlled (e.g. in a fully non-inductive scenario, Vloop = 0).

Summary of changes:
- Added new BC for the psi equation, set by profile_conditions.use_vloop_lcfs_boundary_condition and profile_conditions.vloop_lcfs.
  - Supports the theta method
  - Can be combined with any of the psi initialisation methods:
    - Prescribed psi + Ip_tot rescaling
    - Psi from geometry file
    - Psi from geometry file + Ip_tot rescaling
    - Psi from nu formula + Ip_tot rescaling
  - Added vloop_lcfs to state.CoreProfiles, which is a direct copy from psidot.face_value()[-1].
  - The Vloop BC required minor modifications to compute_boundary_conditions:
    - Renamed to compute_boundary_conditions_for_t_plus_dt
    - Pass in dynamic_runtime_params_slice for t and t_plus_dt
    - Pass in core_profiles_t
- Added psi_right_bc and vloop_lcfs to output.

torax/config/profile_conditions.py

@@ -35,11 +35,18 @@ class ProfileConditions(
 ):
   """Prescribed values and boundary conditions for the core profiles."""
 
-  # total plasma current in MA
+  # Total plasma current in MA
   # Note that if Ip_from_parameters=False in geometry, then this Ip will be
-  # overwritten by values from the geometry data
+  # overwritten by values from the geometry data.
   Ip_tot: interpolated_param.TimeInterpolatedInput = 15.0
 
+  # Boundary condition at LCFS for Vloop ( = dpsi_lcfs/dt )
+  # If use_vloop_lcfs_boundary_condition is True, then the specfied Vloop at
+  # the LCFS is used as the boundary condition for the psi equation; otherwise,
+  # Ip is used as the boundary condition.
+  use_vloop_lcfs_boundary_condition: bool = False
+  vloop_lcfs: interpolated_param.TimeInterpolatedInput = 0.0
+
   # Temperature boundary conditions at r=Rmin. If this is `None` the boundary
   # condition will instead be taken from `Ti` and `Te` at rhon=1.
   Ti_bound_right: interpolated_param.TimeInterpolatedInput | None = None
@@ -175,6 +182,7 @@ class ProfileConditionsProvider(
 
   runtime_params_config: ProfileConditions
   Ip_tot: interpolated_param.InterpolatedVarSingleAxis
+  vloop_lcfs: interpolated_param.InterpolatedVarSingleAxis
   Ti_bound_right: (
       interpolated_param.InterpolatedVarSingleAxis
       | interpolated_param.InterpolatedVarTimeRho
@@ -208,6 +216,8 @@ class DynamicProfileConditions:
   """Prescribed values and boundary conditions for the core profiles."""
 
   Ip_tot: array_typing.ScalarFloat
+  vloop_lcfs: array_typing.ScalarFloat
+  use_vloop_lcfs_boundary_condition: bool
   Ti_bound_right: array_typing.ScalarFloat
   Te_bound_right: array_typing.ScalarFloat
   # Temperature profiles defined on the cell grid.