[UX] Review "apply" and "select action on apply" flow

Created by: danielmarquespt

The flow to choose and apply actions to change sets is not optimal and leads to confusing situations like this

https://sourcegraph.slack.com/archives/CMMTWQQ49/p1656536569702489

Also the apply button is not the primary action of the screen (visually) and is not clear what are the consequences of "apply". The overall flow needs to be reviewed.

Pending a design solution @danielmarques