[DualPorosity] (5/5) Accept the supported dual-continuum keywords

[arturcastiel]

Builds on #7350. Its commit is included in this diff and merges first; review only the last commit here.

What this does

Six keywords stop being rejected: DUALPORO, DUALPERM, NODPPM, SIGMA, SIGMAV,
DPGRID. Nothing else.

Why

Every pull request before this one was inert — parsing, representation, guards and policy, with
the keywords still refused. This is the single change that lets a user run a dual-continuum
deck, which makes it trivial to revert if anything is wrong.

Behavior impact

Flow accepts dual-continuum decks and simulates them.

Testing

The keyword gate in both directions: the six keywords absent from the unsupported list, and a
named subset of the wider family still present.

Requirements and limitations

• Serial only, per the guard added in the previous pull request.
• The matrix-fracture transfer contains no gravity term, so gravity-drainage recovery is not
  represented and those keywords remain rejected.
• Wells should perforate the fracture half. A well completed in the matrix half will produce,
  but it bypasses the transfer this feature exists to model.

[arturcastiel]

jenkins build this please

[arturcastiel]

jenkins build this please with opm-common=5318