encap: Provide default `converged` method.
encap: Provide default `converged` method.

The default computes the maximum (across all nodes) absolute residual
norm as provided by the sweeper, and tests it against
`abs_residual_tol`.

Signed-off-by: Matthew Emmett <edc9e2f987eb312aeebbb11e1edb61666eed223c@gmail.com>

memmett/PFASST,torbjoernk/PFASST,f-koehler/PFASST,memmett/PFASST,selmanTerzi/PFASST,kidaa/PFASST,f-koehler/PFASST,torbjoernk/PFASST,kidaa/PFASST