Rely on resource-registry to close forkers in the forging loop

[jasagredo]

As noted by @nfrisby here, we should be able to use the resource-registry to close the forker. However in the past this lead to a surprising deadlock, seen in the benchmarks.

Both closing them in-place and via the resource-registry should be fairly equivalent. But lets defer this until the node compiles with UTxO-HD again.