bluetooth: Improve quick setting info and add status page to connect devices

The first patches are cleanups and fixes. We then use libbluetooth to expand the information provided by the quick setting and add a status page to connect / disconnect devices. I'll attach screenshots once the styling gets better, I mostly wanted to get this out so people can test with different devices / adapters.

@arun-mani-j Regarding !1433 (merged) . I wonder if we better do our own row type as that would make some things simpler e.g. we can make subtitle a property, can make it work without an actionable widget, etc. I'd also like to introduce an empty state widget as the wifi status page has 3 multiple, bt adds one more and HdyStatusPage would needs CSS to make it look right so we can just as well do a small, status page specific one.

gnome-bluetooth currently doesn't ship C headers so I bundled them. I'll see if we can maybe get them added back at some point. The ABI can't change due to introspection.

Signed-off-by: Guido Günther agx@sigxcpu.org