refactor: move all neighbour list update code to module

src/moves.jl

@@ -57,11 +57,10 @@ Returns the tuple `(e₁, e₂)` of energies before and after the move.
 function perform_action!(system::Particles, action::Displacement)
     neighbour_list = get_neighbour_list(system)
     e₁ = compute_energy_particle(system, action.i, neighbour_list)
+
     update_position!(system, action)
-    c, c2 = old_new_cell(system, action.i, neighbour_list)
-    if c != c2
-        update_neighbour_list!(action.i, c, c2, neighbour_list)
-    end
+    update_neighbour_list!(system, action.i, neighbour_list)
+
     e₂ = compute_energy_particle(system, action.i, neighbour_list)
     action.δe = e₂ - e₁
     return e₁, e₂
@@ -78,10 +77,7 @@ function Arianna.revert_action!(system::Particles, action::Displacement)
     update_position!(system, action)
     neighbour_list = get_neighbour_list(system)
     system.energy[1] -= action.δe
-    c, c2 = old_new_cell(system, action.i, neighbour_list)
-    if c != c2
-        update_neighbour_list!(action.i, c, c2, neighbour_list)
-    end
+    update_neighbour_list!(system, action.i, neighbour_list)
 end
 
 """

src/neighbours.jl

@@ -30,17 +30,10 @@ end
 
 """No-op update for `EmptyList`.
 """
-function update_neighbour_list!(i, c, c2, ::EmptyList)
+function update_neighbour_list!(system::Particles, ::Int, ::EmptyList)
     return nothing
 end
 
-"""Return placeholder old and new cell indices for `EmptyList`.
-
-Always returns (1,1) as no cells are tracked.
-"""
-function old_new_cell(::Particles, i, ::EmptyList)
-    return 1, 1
-end
 
 """Calling an EmptyList objects return an object which can be iterated upon.
 
@@ -169,6 +162,12 @@ function update_neighbour_list!(i, c, c2, neighbour_list::CellList)
     return nothing
 end
 
+function update_neighbour_list!(system::Particles, i::Int, neighbour_list::CellList)
+    c, c2 = old_new_cell(system, i, neighbour_list)
+    if c != c2
+        update_neighbour_list!(i, c, c2, neighbour_list)
+    end
+end
 
 
 
@@ -295,6 +294,13 @@ function update_neighbour_list!(i::Int, c::Int, c2::Int, neighbour_list::LinkedL
     return nothing
 end
 
+function update_neighbour_list!(system::Particles, i::Int, neighbour_list::LinkedList)
+    c, c2 = old_new_cell(system, i, neighbour_list)
+    if c != c2
+        update_neighbour_list!(i, c, c2, neighbour_list)
+    end
+end
+
 """Return old and new cell indices for particle `i` using a `LinkedList` neighbour list.
 """
 function old_new_cell(system::Particles, i, neighbour_list::LinkedList)