async_wrap: call destroy() callback in uv_idle_t

Calling JS during GC is a no-no. So intead create a queue of all ids
that need to have their destroy() callback called and call them later.

Removed checking destroy() in test-async-wrap-uid because destroy() can
be called after the 'exit' callback.

Missing a reliable test to reproduce the issue that caused the
FATAL_ERROR.

PR-URL: https://github.com/nodejs/node/pull/9753
Fixes: https://github.com/nodejs/node/issues/8216
Fixes: https://github.com/nodejs/node/issues/9465


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>