ESP32-C3: Add support for booting from MCUboot bootloader

[gustavonihei]

This PR intends to enable an esp-hal-based Rust application to be booted from the MCUboot bootloader on ESP32-C3.

MCUboot is a secure bootloader solution feature-wise equivalent to the IDF 2nd stage bootloader (current default bootloader). You may find more information on the documentation pages for MCUboot and the Espressif port: https://docs.mcuboot.com/ https://docs.mcuboot.com/readme-espressif.html

Testing

$ cd esp32c3-hal
$ cargo build --release --example hello_world
$ ./test_mcuboot.sh ../target/riscv32imc-unknown-none-elf/release/examples/hello_world

Note

Commit https://github.com/esp-rs/esp-hal/commit/e89ee26acc087296fe7180109f03e8c859b323a8 adds the resources for enabling a quick test of the new feature. It should eventually be dropped.