lvgl: Update to v6.1.2 with performance and UI optimizations

[staff1010]

Description

This PR updates the LVGL library to version 6.1.2 and implements several optimizations and bug fixes for the MKS UI interface. The changes focus on improving UI rendering performance, memory efficiency, and overall user experience.

Key changes include:

• Updated LVGL to v6.1.2 with appropriate buffer size adjustments
• Implemented a hash table system for faster image lookup and rendering
• Fixed SPI flash handling and removed redundant initializations
• Optimized image rendering with configurable drawing parameters
• Added image cache invalidation to fix UI rendering inconsistencies
• Solved the problem mentioned in Fix(cache): Use strcmp for file paths in lv_img_cache_invalidate_src (v6) lvgl/lvgl#8166 lvgl#8166

These modifications result in smoother UI transitions, faster image loading, and better memory management, particularly on TFT35 displays.

Requirements

• Hardware with MKS UI interface
• SPI Flash for image storage

Benefits

• Faster UI rendering and reduced flickering
• More efficient memory usage with optimized buffer management
• Improved image loading performance through hash table implementation
• Fixed image rendering bugs that caused visual artifacts
• Reduced redundant SPI reinitialization for better performance
• Overall more responsive user interface

Configurations

The changes are compatible with existing configurations. No special configuration is required to test these improvements.

Related Issues

• Fixed issue mentioned by Fix(cache): Use strcmp for file paths in lv_img_cache_invalidate_src (v6) lvgl/lvgl#8166 (image rendering issue) lvgl#8166