console hang if user makes a typo while lua is busy

[ab9rf]

The console will hang if the user makes a typo in the console while lua is busy

reproduction:
in the launcher, do lua "while(true) do end" (which tosses lua into an infinite loop)
in the console, type any invalid command and hit enter
the console will deadlock

[ab9rf]

I believe this is caused by the "invalid command" handler calling into help_helper to display help, which requires acquiring a CoreSuspender. We should use a nonblocking lock acquisition approach here and cause help_helper to downgrade gracefully if it cannot acquire a CoreSuspender instead of deadlocking the console.