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.
Changes argument parsing mechanism from argparse to a new one, that provides better support for extensions and options that are only applicable to specific subcommands,
Breaking changes:
1. All global options should go before subcommands, i.e. `idf.py build -C ~/some/project` will not work anymore, only `idf.py -C ~/some/project build` is acceptable
2. To provide multiple values to an option like `--define-cache-entry` it's necessary to repeat option many times, i.e. `idf.py -D entry1 entry2 entry3` will not work, right way is: `idf.py -D entry1 -D entry2 -D entry3`
At the moment there are 3 options like this: `--define-cache-entry` in base list and `--test-components` and `--test-exclude-components` in the unit test extensions
3. Drops `defconfig` and `bootloader-clean` subcommands
Closes https://github.com/espressif/esp-idf/issues/3570
Closes https://github.com/espressif/esp-idf/issues/3571
