Enable LVGL image cache 512KB + header cache 16 for PNG optimization.
Fixes PNG decode bottleneck by caching decoded images in PSRAM.
CONFIG_LV_CACHE_DEF_SIZE=524288
CONFIG_LV_IMAGE_HEADER_CACHE_DEF_CNT=16
On top of font size setting (d8c5a55f).
Removes need for 4KB PSRAM threshold experiment (CONFIG_SPIRAM_MALLOC_ALWAYSINTERNAL=4096) which is deleted.
Adolfo Reyna
b3619d196b