[Uptime UI] Add step selector to waterfall

[katrin-freihofner]

Describe the feature:
Each step details view (waterfall view) should have buttons to navigate to the other steps of this check (only show if there is more than 1 step).

Wireframe

There are three buttons
< navigates to the previous step (if there is one)
> navigates to the next step (if there is one)
Step X of X opens a popover with the list of steps

Wireframe of popover

Please add telemetry support to all 3 buttons (2x arrow and step selector).

Figma file

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[paulb-elastic]

This is done, closing