Improve Kibana tables in error budget explanation panels

For gitlab-com/gl-infra/scalability#1478

Make apdex table use specified target durations

This also makes sure that the urgency fields are included in that table.

Add a Kibana table aggregating apdex & errors

This table uses some painless scripting to show the sum of errors and the slow requests and order by that. This means that stage groups can look at this table and the top endpoint would be the most valuable to work on.

This also needed to make sure that we correctly encode + in the Rison.

Example dasbhoard: https://dashboards.gitlab.net/dashboard/snapshot/KMhcHFmb7p8u5EWJoPEe9SG5OO4rIZSn?orgId=1 (expand "Budget Spend Attribution")