Improving the pipeline list action buttons

This has been bugging me for a while now also, but after criticism from @jschatz1 here: https://gitlab.slack.com/archives/interaction/p1484975325000851 i thought to create this issue.

Currently our buttons are shown like this:

Implementation/Design

• Unify these buttons into 1 big button group, like so:

• color optimize the play button:

• update the icon to be inline with the pipeline graph, resulting in:

@tauriedavis @filipa what do you think?