Events can be added to buffer despite the session being expired

[billyvg]

~Still investigating, but we are getting event buffer issues because expired sessions are not properly ending the session.~ handleException is causing a possible infinite loop of sorts for expired sessions. it eventually ends up calling addEvent() which only checks if replay is paused or ended and not if session is valid. This causes a buildup in the buffer.

e.g. user idles on the page and replay continues to try to flush after the session has ended. Session is not ending properly so buffer continues to grow in size and continues to flush.

This also causes a replay with canvas recordings because resets will cause a new web worker to initialize leading to browser crashes (Closes: https://github.com/getsentry/sentry-javascript/issues/13743)