[ML] Single metric viewer - time slider hidden when expanded to full width

[pheyos]

Found in version

• 7.5.1-bc2

Browser

• Chrome

Steps to reproduce

• In the single metric viewer expand the time slider to the full width

Expected result

• There is an obvious way for the user to further change the selected time range with the slider.

Actual result

• The time slider handles are hidden and it's not obvious how to get them back (you can by dragging the invisible handle on the far left or the far right or by clicking one of the time range links):
  

Additional information

• In 6.8 the time slider is still displayed when expanding to the full width.

[elasticmachine]

Pinging @elastic/ml-ui (:ml)