Services legend clean-up

[jasonrhodes]

Service legend should only show services in current transaction view

• Service legend should only show services that appear in the currently viewed transaction and not for the entire trace

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Add Services label in front of services legend

Example from design

• Add Services label in front of services legend

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Include services legend in the locked element when scrolling a large timeline

The current Timeline locks the x-axis to the top so it's easy for the user to see the durations as they move down a big timeline visualization. I would like to suggest we include the services legend as well, so users can tell which services are referred to without having to scroll back up.

Example of existing functionality

• Expand locking header to include the services legend

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[elasticmachine]

Pinging @elastic/apm-ui