[DualPorosity] (4/5) Apply the dual-continuum policy and twin co-location

[arturcastiel]

Builds on OPM/opm-common#5318, which must merge before this compiles.

What this does

Applies the dual-continuum policy in the simulator. The complete face policy in one place — a
face between a matrix cell and a fracture cell never carries flow, because the coupling is the
input non-neighbour connection; matrix-matrix faces flow only under dual permeability; fracture
permeability is scaled unless the run disables it; twin couplings are exempt from the
non-neighbour prune. Fracture cells are treated as physically co-located with their matrix twin
in equilibration, cell-centre depths and the result writer.

Why

The input layer for this landed in opm-common; this is the consumer.

Two fixes ride along because they are the same story. The input grid is now bound inside its
guard at every site rather than unconditionally — the parallel state object throws for non-zero
ranks, so the unguarded pattern reached that throw on every multi-process run. And twin
classification is derived from the Cartesian dimensions rather than the input grid: the same
arithmetic without a rank-0 dependency, following the read-and-broadcast convention this file
already uses a few lines below for the pinch options.

Behavior impact

None yet — the keywords are still rejected. The switch is the next pull request.

Testing

Face policy: cross-half faces zero, matrix-matrix under dual permeability, permeability scaling
on and off, and dual-permeability half-equivalence against single-porosity analogues. Twin
couplings surviving the non-neighbour prune, with a case at more than one matrix layer — where
the twin offset stops coinciding with the neighbour offset and the exemption is genuinely
exercised.

Requirements and limitations

Serial only. Measured: at two processes none of nine twin pairs separated across ranks; at
four processes at least four of nine did. Rather than silently drop couplings, a dual-continuum
run at more than one process stops with a located error. The design does not preclude parallel
support later; the guard is the honest state today.

[arturcastiel]

jenkins build this please

[arturcastiel]

jenkins build this please with opm-common=5318