Bingo! Known issue of the library: the mbedtls_md5_starts() was removed from the orginal md5.h · Issue #1149 · me-no-dev/ESPAsyncWebServer · GitHub. The update of mbedtls (with its associated function names) seems to have broken a bunch of libraries using it.
Someone filed a fix PR at Fix compiler error for ESP32-C3 and mbed TLS v2.7.0+ by khoih-prog · Pull Request #970 · me-no-dev/ESPAsyncWebServer · GitHub. In your platformio.ini, replace your previous me-no-dev/ESP Async WebServer@^1... line with https://github.com/khoih-prog/ESPAsyncWebServer/archive/refs/heads/master.zip. Does it get any better?
Note: Another ‘fix’ is to not use the new Arduino-ESP32 core that breaks these libraries. For that, revert to an older platform version in the platformio.ini.
platform = espressif32@3.5.0