Swarm: Add continuous DM argument to DMSwarmProjectFields()

doc/changes/dev.rst

include/petscksp.h

src/binding/petsc4py/src/petsc4py/PETSc/DMSwarm.pyx

src/binding/petsc4py/src/petsc4py/PETSc/petscdmswarm.pxi

src/dm/impls/swarm/tests/ex2.c

src/dm/impls/swarm/tutorials/ex1.c

src/dm/tutorials/ex21.c

src/ksp/ksp/tutorials/ex70.c

src/ksp/ksp/utils/dm/dmproject.c