[Flow] Improve Pause Action Coverage

[jasonLaster]

We've had some great help adding types to source maps utils. It would be really helpful to begin taking a look at our Action's types.

The pause action currently does not have any flow types and could use the most help.

I took a look at the debugger flow report and noticed an interesting difference between the pause and sources actions. I believe the difference in coverage is due to the action types being specified for sources, but not for pausing.

[jasonLaster]

this is a dupe of #1004