feat: use physical volume buttons to capture photo

[budowski]

Closes #2212

[albullington]

This is working well for me in StandardCamera. Let's add this to the AICamera too so users have a consistent experience across our product -- I think users will be incredibly confused if they can use these buttons in one camera but not the other.

[albullington]

This is close, but currently tapping the AI Camera volume button navigates twice, not once, which means Suggestions is getting pushed onto the stack twice in a row. We need to make sure all the functionality related to taking a photo is only handled once, so we're not accidentally saving duplicate photos to the camera roll, making extra observations, or navigating multiple times.