Using ESP-IDF bootloader as a temporary runtime

[MabezDev]

Compared to most chips, the esp32 is quite complicated. Building a run time in pure Rust will take some time. Angus on the esp32 forum suggested a great idea to use the boot loader as a starting point, as this takes care of a lot of initialisation.

We could develop our Rust implementation behind a feature gate and swap the boot loader out when we are happy with it.