Use bootloader settings for esp32

[UncleGrumpy]

Changes harcoded settings to use defaults that can be set using idf.py menuconfig and read from the bootloader by esptool when flashing an esp32 device.

• Automatically detect chip by default.
• Add support for custom flash modes (qio, qout, etc...)
• Add support for custom flash speeds (26m, 80m, etc...)

[petermm]

let's merge! battle-proven in atomvm_rebar3 plugin..

supercedes https://github.com/atomvm/exatomvm/pull/3 which was mistakenly closed..