Kernel+SystemMonitor: Show VM region "shared" and "stack" bits in UI

Expose these two region bits through /proc/PID/vm and show them in the
SystemMonitor process memory map view.

Applications/SystemMonitor/ProcessMemoryMapWidget.cpp

@@ -22,6 +22,10 @@ ProcessMemoryMapWidget::ProcessMemoryMapWidget(GWidget* parent)
             builder.append('R');
         if (object.get("writable").to_bool())
             builder.append('W');
+        if (object.get("shared").to_bool())
+            builder.append('S');
+        if (object.get("stack").to_bool())
+            builder.append('T');
         return builder.to_string();
     });
     pid_vm_fields.empend("name", "Name", TextAlignment::CenterLeft);

Kernel/FileSystem/ProcFS.cpp

@@ -258,6 +258,8 @@ Optional<KBuffer> procfs$pid_vm(InodeIdentifier identifier)
         auto region_object = array.add_object();
         region_object.add("readable", region.is_readable());
         region_object.add("writable", region.is_writable());
+        region_object.add("stack", region.is_stack());
+        region_object.add("shared", region.is_shared());
         region_object.add("address", region.vaddr().get());
         region_object.add("size", (u32)region.size());
         region_object.add("amount_resident", (u32)region.amount_resident());