window: Overhaul UI for GNOME Circle

As part of Binary entering GNOME Circle, a UI overhaul was recommended by @gregorni to better accommodate the base selectors and the bit counter. This also makes both input boxes mutable, and makes Binary it a bit better on mobile devices. I've also taken the opportunity to convert items and functions to being named under snake_case format, to be more consistent with Python and GNOME standards. It's also easier to accomodate AdwDialog in this design, even if the UX isn't ideal still.

Before: After:

Marking this as draft for now, because while it's still a functional build of the app, it's still designed on the mutable input/immutable output and these UX changes should be made before merging it fully:

[x] Dynamically switch the active bit counter, and show both when both inputs are used.
[x] The swap button isn't really needed anymore, and should maybe just be an image (if it exists at all). I could be convinced to keep it though.
[x] The image used in place of a swap button should be two vertical arrows, rather than horizontal ones.
[x] Dropdown visibility should only be affected by change_bases().
[x] Bottom entry should follow the error/mono style classes appropriately. This will be done the easiest by moving this into input_handler() and output_handler()
[x] Change the behaviour of automatically changing bases such that the unchanged base is updated
[x] Changing the bottom input should actually change the top value. This probably requires a more in-depth overhaul of the input_handler() feature.
[x] Case is inconsistent between top and bottom entries. Bottom entry is always caps lock, but this doesn't apply to the top one. Ideally the bottom entry won't care, but both being caps should be fine failing that.

fizzyizzy05 / binary

window: Overhaul UI for GNOME Circle #14