feat: update chart to coder 1.21.0

Updates the chart for Coder 1.21.0.
The vast majority of these changes come from the upstream chart.
The routing for this application has changed, and therefore the the Istio Virtual Service has been greatly simplified. I added a new VS in the event a user configures the coder.devurlsHost value.

I have tested this on my local cluster and a cluster built as part of the Volta bootstrap.