kokkos(ext): graph resubmission made nicer with the box

[romintomasetti]

From ideas in:

• kokkos(ext): resubmit graph until #291

[maartenarnst]

Just noting that in the thoughts about API, I was thinking in the direction of

stdexec::sync_wait(
    exec::repeat_effect_until(
        starts_as_graph_on(escs, std::move(chain)) | ...
    )
);

[maartenarnst]

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | on(gsc{exec}, just() | then() | then() ) | then()
    )
);

[maartenarnst]

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | on(graph_sched(exec), just() | then() | then() ) | then()
    )
);

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | on_memoize(graph_sched(exec), just() | then() | then() ) | then()
    )
);

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | memoized_on(graph_sched(exec), just() | then() | then() ) | then()
    )
);

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | as_graph_on(exec, just() | then() | then() ) | then()
    )
);

[maartenarnst]

stdexec::sync_wait(
    just() | then() | exec::repeat_effect_until(
        just() | on(graph_sched(exec), memoize(just() | then() | then()) ) | then()
    )
);

[maartenarnst]

Hey @romintomasetti. How about sender_ref for the box?