*: make generation configurable, use sdkconfig defaults

This moves badge hardware generation selection over from a header file
into ESP-IDF configuratbility.

The generaiton can now be selected by specifying `BADGE_GENERATION` or
`-g` when running the initial built.

In addition, each generation now gets its own sdkconfig.defaults file
(instead named sdkconfig.$generation) and the big autogeneration
sdkconfig file gets yeeted.