Fix M5Stack Tab5 ST7121/ST7123 display detection

[78]

Summary

• reset the LCD and touch controller through PI4IOE before panel detection
• read the ST712x touch firmware version to distinguish ST7121 from ST7123
• add the Apache-2.0 ST7121 driver and panel-specific initialization timing used by M5Stack
• enable the ESP-IDF 6 DMA2D path while retaining the ESP-IDF 5 compatibility flag
• prefer PSRAM for the ESP-Hosted mempool on both Tab5 variants
• document the supported panel variants and add regression coverage

Fixes #2186.
Supersedes #2196.

Validation

• python3 -m unittest discover -s scripts/tests -v: 68 passed
• ESP-IDF 6.0.2 build: m5stack-tab5
• ESP-IDF 6.0.2 build: m5stack-tab5-p4x
• clang-format and git diff checks passed

Hardware validation

Not performed in this environment. Before marking this PR ready, please cold-boot smoke-test ST7121, ST7123, and ILI9881C/GT911 Tab5 units.