Highlight selected span

[jorgeepc]

Describe the enhancement you'd like to see
In our current graph view, we highlight the selected span by using a blue line around the span. However, it is not easy no identify it specially when you are in the "Test Spec" detail mode. We want to improve this design to have a clear understanding of which span is selected.

Additional context

[olha23]

@jorgeepc i propose use more wider stroke and drop shadow like this:

check the mockups here: https://www.figma.com/file/LBN4SKVPq3ykegrPKbHT2Y/0.8-0.9-Release-Tracetest?node-id=2588%3A34470&t=WbaRDtQAN8PdWHLL-1