ota: detect Tasmota magic numbers when booting (#2370)
- inject dummy data sequence that is expected to hold current version info
- check rtcmem markers and purge settings, since we don't want accidentally reading something as a kv
- sometimes we cannot boot b/c of certain SDK params, purge last 16KiB as well
ref. `SetOption78 1`
https://tasmota.github.io/docs/Commands/#setoptions
The original idea from Esphome:
0e59243b83/esphome/core/esphal.cpp (L275-L287)
Does not seem to be working atm. Will need to re-check with the esphome builder, c/p did not work and I tried building with gcc-10
Specific things we want to do is to have 'version' byte between 2 'marker' bytes:
217addc2bb/tasmota/settings.ino (L218-L262)
0dfa38df89/tasmota/i18n.h (L780-L782)