This updates the minimal supported version of CMake to 3.16, which in turn enables us to use more CMake features and have a cleaner build system.
This is the version that provides most new features and also the one we use in our latest docker image for CI.
Add the possibility to have user bootloader components. This is performed
from an application/project, by creating bootloader components. To do so,
it is required to create a `bootloader_component` directory containing
the custom modules to be compiled with the bootloader.
Thanks to this, two solutions are available to override the bootloader now:
- Using hooks within a user bootloader component
- Using a user defined `main` bootloader component to totally override the
old implementation
Please check the two new examples in `examples/custom_bootloader`
* Closes https://github.com/espressif/esp-idf/issues/7043
