fix: Replace Date.now() with performance.now()

[CptLemming]

When using WebsocketClientTransport I've noticed if a users local clock gets adjusted, a connection timeout is triggered:

No keep-alive acks for 30000 millis WebsocketDuplexConnection: Socket closed unexpectedly

This is caused by keeping track of timeout with Date.now() which doesn't account for clock skew.

See https://developer.mozilla.org/en-US/docs/Web/API/Performance/now#performance.now_vs._date.now