Granite.Clamp

### Problem

Something I’m having to add LibAdwaita for basically every repo is Adw.Clamp. This container widget allows you to set a maximum width whereas Gtk only allows you to set a minimum width. This is super helpful for making sure lists for example can be scaled down, but don’t continue to fill horizontal space on super large monitors which ends up making them more difficult to use

### Proposal

We should probably have a Clamp implementation so we don’t need to add a dep just for this feature if Adw isn’t needed otherwise

While we’re at it I’d like to look into why Adw uses pixels instead of chars for it’s values

### Prior Art (Optional)

Adw.Clamp! It’s Clamp. It’s got the juice! https://valadoc.org/libadwaita-1/Adw.Clamp.html