misc changes

* draw_text_string_pos_extent_zoomed can now oversample text futher (if desired)
* render_ui_via_box_tree has a rudimentary render pass layering optimization

Add support for the slab allocator to accept arbitrary alignments (odin's map container needs it)
Messing around with 64-byte alignment as the default for the allocator...

code/sectr/app/state.odin

@@ -154,11 +154,14 @@ AppConfig :: struct {
 
 	engine_refresh_hz : uint,
 
+
 	timing_fps_moving_avg_alpha : f32,
 
 	ui_resize_border_width : f32,
 
 	color_theme : AppColorTheme,
+
+	font_size_canvas_scalar : f32,
 }
 
 AppWindow :: struct {