Show start & stop button for trained models in ML

[philippkahr]

Kibana version: 8.3.3

Describe the bug:

I was wondering how I can stop a trained ML model. I discovered a weird blue box that looked like a stop symbol when hovering over the model near the ... symbol. It feels weird to get a greyed out mouse with a block symbol, when there isn't something clickable.

Can we opt to show the play and stop button always?

https://user-images.githubusercontent.com/12175559/183851763-bb9e7220-584f-483b-8ba0-5764a7251650.mov

[elasticmachine]

Pinging @elastic/ml-ui (:ml)