Add ESP32-S31 as a supported target for the H.264 encoder/decoder
example and bump the esp_h264 component to v1.3.8, which provides
support (prebuilt software library) for ESP32-S31.
- Add sdkconfig.defaults.esp32s31 with SPIRAM/CPU settings
- Update pytest and build-test-rules to cover esp32s31
- Update README and Kconfig help text