Use new libadwaita 1.4 widgets
Before
After
Please note that I'm currently learning C hence I'm not very proficient in it. I created this MR after seeing Christian's mastodon post, maybe it can serve as a basis towards porting to the new libadwaita widgets. Everything works correctly on my end, but I recommend double checking
note that I made the design decision to move the refresh button to the headerbar, to make the app look more consistent with others.
Also, the app is currently not very adaptive as DspyMethodView
is too dense and can expand, making D-Spy too large for mobile devices.