Get icon spacing from stylesheet

Right now the icon spacing in the panel between the mic and volume icons is hardcoded. For future proofing, we should get this value from the `padding` of `.composited-indicator`

Search the panel code for the hardcoded spacing between the mic and volume icons, then find the stylesheet rule for `.composited-indicator`. Confirm how its `padding` is represented and verify that the icon spacing follows that value rather than a separate constant. The issue is done when stylesheet padding controls the spacing.

Written by the indexing model from the issue text.