Fixes #784.

Commit 6ea23df ("window: do not unfocus on new window") imported the
Metacity bf17c79 / Mutter 998d921d behavior for GNOME Bugzilla #773210:
when a new transient maps without taking focus, keep focus on the parent
so GTK popup and completion windows and VLC fullscreen controls do not
steal keyboard focus.

That blanket change also affected modal dialogs whose parent already has
focus. Electron and GTK file chooser dialogs can reach
meta_window_show() with takes_focus_on_map false because their
_NET_WM_USER_TIME is missing or stale. Since 6ea23df, such dialogs are
mapped above the parent but keyboard focus stays on the parent, so
typing goes to the wrong window.

Keep the bf17c79-equivalent behavior for non-modal transients, but when
the new window is a META_WINDOW_MODAL_DIALOG whose ancestor is the
current focus window, force takes_focus_on_map so the blocking dialog
receives keyboard focus immediately.

When using switch-windows-all to cycle through windows across all
workspaces, marco was grouping windows by workspace rather than using
a global MRU (most-recently-used) list. This caused several issues:

- Sticky windows appeared multiple times, once per workspace
- Window order was confusing (since they were grouped by workspace number)
- Behavior was different from other window managers

Fixed by collecting all windows, sorting them by recency, then building
the tab list from this global list.

Fixes #286

pass focus to window if it is on another workspace

Corner-tiled windows were being treated as maximized horizontally, which
is wrong. Instead, we clear all maximized flags to make sure their size
is respected on reload.

Fixes #710