Access tab improvements

We’ve shipped some subtle but important simplifications to the Access tab for feature flags. Here’s what has changed:

• Moved stage picker into the sidebar - So it’s out of the way of the main area for access control.
• Added stage picker to confirmation dialog - We found that after making access changes that involved moving the feature to the next stage of its lifecycle, we’d sometimes forget to update the stage. Because of that, the stage picker now appears in the confirmation dialog once you’re ready to save the access changes you’ve made.
• Showing access history in targeting - We’ve had flag access version history for a while, but it was hidden away. To make it more accessible, we’re now listing the version history below the targeting area on the Access tab.