Custom font set function (#2261)

* custom font set function
* update API symbols
* add example of custom font usage
* delete u8g2 dependency in example custom font
* rename to canvas_set_custom_u8g2_font
* now change the name in ALL places

Co-authored-by: あく <alleteam@gmail.com>
Co-authored-by: hedger <hedger@users.noreply.github.com>

applications/debug/example_custom_font/application.fam

@@ -0,0 +1,9 @@
+App(
+    appid="example_custom_font",
+    name="Example: custom font",
+    apptype=FlipperAppType.EXTERNAL,
+    entry_point="example_custom_font_main",
+    requires=["gui"],
+    stack_size=1 * 1024,
+    fap_category="Debug",
+)