ServiceWorker and Reproducibility Improvements

[ikreymer]

for wombat.js based replay:

• If loading from SW, override unregister() to prevent unregistering existing SW in the replay

reproducibility:

• timezone: override Date.getTimeZoneOffset(), Date.toString(), Date.toTimeString() for consistent replay
• referrer: set referrer to empty for top replay frame (otherwise maybe top-frame or custom based on embed), or rewrite existing referrer for nested frame
• URL parsing: use URL for parser if available, fallback to anchor tag if not. set origin to null if no host (safari uses :// by default)
• support blob: urls for replay frame, don't rewrite