This commit makes the Windows Terminal play an audible sound when the
`BEL` control character is output.
The `BEL` control was already being forwarded through conpty, so it was
just a matter of hooking up the `WarningBell` dispatch method to
actually play a sound. I've used the `PlaySound` API to output the sound
configured for the "Critical Stop" system event (aka _SystemHand_),
since that is the sound used in conhost.
## Validation
I've manually confirmed that the terminal produces the expected sound
when executing `echo ^G` in a cmd shell, or `printf "\a"` in a WSL bash
shell.
References:
* There is a separate issue (#1608) to deal with configuring the `BEL`
to trigger visual forms of notification.
* There is also an issue (#2360) requesting an option to disable the
`BEL`.
Closes#4046
09cc5f492c