[lvgl] Migrate lv_font creation into Font class and optimise (#11915)

tests/components/lvgl/lvgl-package.yaml

@@ -76,7 +76,7 @@ lvgl:
       line_width: 8
       line_rounded: true
     - id: date_style
-      text_font: roboto10
+      text_font: !lambda return id(roboto10);
       align: center
       text_color: !lambda return color_id2;
       bg_opa: cover
@@ -267,7 +267,7 @@ lvgl:
               snprintf(buf, sizeof(buf), "Setup: %d", 42);
               return std::string(buf);
             align: top_mid
-            text_font: space16
+            text_font: !lambda return id(space16);
         - label:
             id: chip_info_label
             # Test complex setup lambda (real-world pattern)

tests/components/lvgl/test.host.yaml

@@ -18,6 +18,7 @@ touchscreen:
 
 lvgl:
   - id: lvgl_0
+    default_font: space16
     displays: sdl0
   - id: lvgl_1
     displays: sdl1
@@ -39,3 +40,8 @@ lvgl:
                 text: Click ME
           on_click:
             logger.log: Clicked
+
+font:
+  - file: "gfonts://Roboto"
+    id: space16
+    bpp: 4