BUG: PETSc interface change has broken VertexOnlyMesh

[dham]

Describe the bug
This change to PETSc has changed the interface to DMSwarm such that the cell ID field has changed.

Steps to Reproduce

Using current Firedrake and PETSc main:

from firedrake import *
msh = UnitSquareMesh(5,5)
VOM = VertexOnlyMesh(msh, vertexcoords=msh.coordinates.dat.data, redundant=False)

Produces:

   3880     # NOTE ensure that swarm.restoreField is called for each field too!
   3881     swarm_coords = swarm.getField("DMSwarmPIC_coor").reshape((num_vertices, gdim))
-> 3882     swarm_parent_cell_nums = swarm.getField("DMSwarm_cellid").ravel()
   3883     field_parent_cell_nums = swarm.getField("parentcellnum").ravel()
   3884     field_reference_coords = swarm.getField("refcoord").reshape((num_vertices, tdim))

petsc4py/PETSc/DMSwarm.pyx in petsc4py.PETSc.DMSwarm.getField()

Error: error code 83
[0] DMSwarmGetField() at /tmp/petsc-src/src/dm/impls/swarm/swarm.c:1663
[0] DMSwarmDataBucketGetDMSwarmDataFieldByName() at /tmp/petsc-src/src/dm/impls/swarm/data_bucket.c:172
[0] Cannot find DMSwarmDataField with name DMSwarm_cellid

Additional behaviour

It appears that the cell id is no longer stored in the hard-coded name "DMSwarm_cellid" but instead the name has to be accessed programatically. It's not clear how to do that from Python (and the interface may not have been exposed).