BUG: MeshHierarchy with ref_per_level=3 fails

[APaganini]

Describe the bug
In MeshHierarchy, users can specify how many refinement_levelsand how many refinements_per_level they want. If refinements_per_level is not 1, 2, or 4 (or probably any power of 2), then restrict and prolong raise a KeyError (it seems because there's a mismatch with the number of dofs).

Steps to Reproduce
This minimal example

from firedrake import *

mesh = UnitSquareMesh(2,2)

for n in range(1, 6): 
    print("\nrefinements_per_level = ", n)

    # refinement_levels=1, refinements_per_level=n
    mh = MeshHierarchy(mesh, 1, n)

    # Coarse space
    V_coarse = FunctionSpace(mh[0], "CG", 2)
    V_coarse_dual = V_coarse.dual()

    # Fine space
    element = V_coarse.ufl_element()
    V_fine = FunctionSpace(mh[-1], element)
    V_fine_dual = V_fine.dual()

    # restrict cofunction from V_fine_dual to V_coarse_dual
    F_fine = Cofunction(V_fine_dual)
    F_coarse = Cofunction(V_coarse_dual)
    try:
        restrict(F_fine, F_coarse)
        print("restrict works")
    except Exception as e:
        print("restrict does not work, the error is:")
        print(e)

    # prolong function from V_coarse into V_fine
    u_coarse = Function(V_coarse)
    u_fine = Function(V_fine)
    try:
        prolong(u_coarse, u_fine)
        print("prolong works")
    except Exception as e:
        print("prolong does not work, the error is:")
        print(e)

outputs

refinements_per_level =  1
restrict works
prolong works

refinements_per_level =  2
restrict works
prolong works

refinements_per_level =  3
restrict does not work, the error is:
Fraction(54043195528445951, 54043195528445952)
prolong does not work, the error is:
Fraction(6004799503160661, 18014398509481984)

refinements_per_level =  4
restrict works
prolong works

refinements_per_level =  5
restrict does not work, the error is:
Fraction(90071992547409921, 90071992547409920)
prolong does not work, the error is:
Fraction(3602879701896397, 18014398509481984)

Expected behavior
From the documentation, this should work with any integer value.

Error message
here is one of the backtraces:

Traceback (most recent call last):
  File "/Users/alberto/Documents/FIREDRAKE/firedrake/src/firedrake/firedrake/mg/kernels.py", line 224, in prolong_kernel
    return cache[key]
           ~~~~~^^^^^
KeyError: ('prolong', (0, (0,), (1,), (2,)), (1, (3,), (4,), (5,)), (2, ()), (0, (0,), (1,), (2,)), (1, (), (), ()), (2, ()))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/alberto/Documents/FIREDRAKE/fireshape/examples/levelset/multigridfail.py", line 32, in <module>
    prolong(u_coarse, u_fine)
  File "petsc4py/PETSc/Log.pyx", line 188, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func
  File "petsc4py/PETSc/Log.pyx", line 189, in petsc4py.PETSc.Log.EventDecorator.decorator.wrapped_func
  File "/Users/alberto/Documents/FIREDRAKE/firedrake/src/firedrake/firedrake/mg/interface.py", line 75, in prolong
    kernel = kernels.prolong_kernel(coarse)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/alberto/Documents/FIREDRAKE/firedrake/src/firedrake/firedrake/mg/kernels.py", line 282, in prolong_kernel
    "ncandidate": hierarchy.fine_to_coarse_cells[levelf].shape[1],
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
KeyError: Fraction(6004799503160661, 18014398509481984)

Environment:

• Output of `firedrake-status

(firedrake) (ap/reenable_multidgridcontrolspace *)$ firedrake-status
/Users/alberto/Documents/FIREDRAKE/firedrake/bin/firedrake-status:4: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
 __import__('pkg_resources').require('firedrake==0.13.0+5908.g1692a70c7')
Firedrake Configuration:
   package_manager: True
   minimal_petsc: False
   mpicc: None
   mpicxx: None
   mpif90: None
   mpiexec: None
   disable_ssh: True
   honour_petsc_dir: False
   with_parmetis: False
   slepc: False
   packages: []
   honour_pythonpath: False
   opencascade: False
   tinyasm: False
   torch: False
   petsc_int_type: int32
   cache_dir: /Users/alberto/Documents/FIREDRAKE/firedrake/.cache
   complex: False
   remove_build_files: False
   with_blas: download
   netgen: False
Additions:
   None
Environment:
   PYTHONPATH: None
   PETSC_ARCH: None
   PETSC_DIR: None
Status of components:
---------------------------------------------------------------------------
|Package             |Branch                        |Revision  |Modified  |
---------------------------------------------------------------------------
|FInAT               |master                        |f493084   |False     |
|PyOP2               |master                        |d017d594  |False     |
|fiat                |master                        |e440a06   |False     |
|firedrake           |master                        |1692a70c7 |False     |
|h5py                |firedrake                     |6cc4c912  |False     |
|libspatialindex     |master                        |4768bf3   |True      |
|libsupermesh        |master                        |dbe226b   |False     |
|loopy               |main                          |8158afdb  |False     |
|petsc               |firedrake                     |98a9995288|False     |
|pyadjoint           |master                        |cefba3f   |False     |
|pytest-mpi          |main                          |a478bc8   |False     |
|tsfc                |master                        |47c1324   |False     |
|ufl                 |master                        |cf66c4b3  |False     |
---------------------------------------------------------------------------