Scrub zooming broken on charts

[igoristic]

Zooming (via scrub) is now broken since the selected range is the offset, but we're sending those same values as UTC

To reproduce:

1. Enable monitoring data and let it collect for at least 5-10min
2. Set your timezone to something other than your local/browser (I'm at America/New_York but set my Kibana timezone to America/Los_Angeles)
3. Go to one of the rhythmic charts and scrub from the beginning portion of the collected data

This might be a regression from #45949

[elasticmachine]

Pinging @elastic/stack-monitoring (Team:Monitoring)

[chrisronline]

Nice catch! I think you might have mentioned it in the original PR, and I thought I tested it but it might have been only with the Browser time zone. I'm looking into this now