feat: reorder tabs via left mouse drag
Relates to #549
Be able to reorder tabs within a window via left mouse drag. Doesn't have animation dragging (like on Konsole), so it looks snappy for now.
I tested this commit on Fedora KDE and Windows. This feature works on both platforms.
I tried on macOS as well, but couldn't get wezterm to compile from source. Maybe it works for someone else who can try it?
Edit: after reinstalling XCode Command Line tools, wezterm compiles on my mac. The tab dragging feature works on macOS as well.
I've tested this on macOS, it works well!
The tabs aren't draggable with config.window_decorations = "INTEGRATED_BUTTONS", but that's because of #7116 and not a deficiency with this PR.