Disable leak listener for stable build

[jrieken]

We have the leak listener in place and the question if we (1) disable it for the stable build or (2) make it more lightweight. Currently, it always captures the current stack when registering a listener. This cost around 0.1-1ms and takes up some storage. Also, not sure about the value of listener leak warning in the console of stable build. We could

• leave it as is
• disable it for stable
• have a simpler version, like Node.js, which only shows a count once