crypto: add newline to cert and key if not present

After one of OpenSSL updates we have stopped accepting PEM private keys
and certificates that doesn't end with a newline (`\n`) character.
Handle this regression in `crypto.js` to make less trouble to our users.

fix #6892
path: improve POSIX path.join() performance

Performance gains are ~4x (~1.5us), but still much slower than a naive
approach. There is some duplicate work done between join(), normalize()
and normalizeArray() so additional optimizations are possible.

Note that this only improves the POSIX implementation.

Thanks to @isaacs and @othiym23 for helping with this optimization.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
node: only run same AL once on error

Should have been included with 60fcc11 as it is the same type of fix.

Signed-off-by: Forrest L Norvell <ogd@aoaioxxysz.net>
node: remove asyncStack

Now that the context stores the active execution stack, and because
removeAsyncListener() always removed the AsyncListener from the queue
and the stack, there's no need to keep a stack around anymore. Instead
the active asyncQueue and the currentContext is able to handle it all.

Signed-off-by: Forrest L Norvell <ogd@aoaioxxysz.net>