ecore_wl2_window: add code to handle pending min/max size

ecore_wl2_window: add code to handle pending min/max size

There was a bug that the minimum or maximum size didn't work when the user calls
ecore_wl2_window_minimum_size_set() before calling ecore_wl2_window_show().

So, we add a pending min/max size to resolve this issue.
If the xdg_toplevel or zxdg_toplevel is not created, then we save the min/max size.
And then, after creating zxdg_toplevel, we apply the pended min/max size to the window.

Change-Id: I2c9404db18f13afabd7c51e6d15935bd230e27a9