sim: sim-close: unify sim_close logic

sim: sim-close: unify sim_close logic

Other than the nice advantage of all sims having to declare one fewer
common function, this also fixes leakage in pretty much every sim.
Many were not freeing any resources, and a few were inconsistent as
to the ones they did.  Now we have a single module that takes care of
all the logic for us.

Most of the non-cgen based ones could be deleted outright.  The cgen
ones required adding a callback to the arch-specific cleanup func.
The few that still have close callbacks are to manage their internal
state.

We do not convert erc32, m32c, ppc, rl78, or rx as they do not use
the common sim core.