libsysprof-ui: land new UI design

This comprises a massive rewrite of the UI for browsing captures. We use
the SysprofAid class to scan capture files for content and then auto-
matically add visualizers and details pages.

To avoid breaking things incrementally, we just land this as a very large
commit. Not necessarily ideal, but given the amount of stuff that could
break, this is easier.

As part of this process, we're removing a lot of the surface API so that
we can limit how much we need to maintain in terms of ABI.

src/libsysprof-ui/sysprof-notebook.h

@@ -20,6 +20,10 @@
 
 #pragma once
 
+#if !defined (SYSPROF_UI_INSIDE) && !defined (SYSPROF_UI_COMPILATION)
+# error "Only <sysprof-ui.h> can be included directly."
+#endif
+
 #include <gtk/gtk.h>
 #include <sysprof.h>