Wait for the toolchange temperature on the wipe tower

Adds a printer option that picks up the new tool without a blocking temperature
wait, travels to the wipe tower, and waits there right before purging, parked
beside the tower so the ooze from the heat-up lands next to it rather than on the
model. The incoming filament's target is raised ahead of the tool change, so the
heat-up overlaps both the change itself and the travel to the tower.

Off by default, and only offered for multi-extruder printers using a Type 2 wipe
tower; the generic toolchanger profile enables it.

src/libslic3r/PrintConfig.hpp

@@ -1660,6 +1660,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionBool,                purge_in_prime_tower))
     ((ConfigOptionBool,                enable_filament_ramming))
     ((ConfigOptionBool,                tool_change_on_wipe_tower))
+    ((ConfigOptionBool,                wait_for_temp_on_wipe_tower))
     ((ConfigOptionBool,                support_multi_bed_types))
     ((ConfigOptionBool,                use_3mf))