Fix examples for LVGL v8

[amirgon]

Fix examples under examples/ dir to work with LVGL v8.

https://github.com/lvgl/lv_binding_micropython/tree/dev-8.0/examples

• [x] advanced_demo.py
• [x] custom_widget_example.py
• [x] uasyncio_example1.py
• [x] example1.py
• [x] example2.py
• [x] example3.py
• [x] ~chart_anim_example.py~ Removed example.
• [x] Dynamic_loading_font_example.py
• [x] fb_test.py
• [x] png_example.py
• [ ] tpcal.py