don't clean away Agraphinfo_t in layout specific cleanups

don't clean away Agraphinfo_t in layout specific cleanups

This cleanup is since 2b3b37c47244f57a9690bff8fb92f77d17ec616c handled
by the general `graph_cleanup` function.

This information is since 44b02b91bd156cb832894fb4948bf4bc75ab27cb
needed by the general layout cleanup function that runs after the
layout-specific cleanup.

This problem was fixed for root graphs in commit
c55b546e3965a8dfd2a66763961c4a8003e433bf, but not for subgraph layout.

This fixes a heap-buffer-overflow detected by ASan in the
test_neatopack test, which now runs without failures.

This commit also reverts commit
291b7a40f742551797e5681acbb8f5662c084822 since the
dot.demo/neatopack.c example now runs without failures.

Fixes https://gitlab.com/graphviz/graphviz/-/issues/1800.