feature: replace test mode with bitaxe-raw compatible mode

[skot]

Instead of having test mode run the tests directly from the ESP32, I think it would be more helpful/versatile to have test mode be a bitaxe-raw compatible interface. Then what ever tests developers/manufacturers/troubleshooters would like to run, could be run from a USB connected PC. Tests could prolly even be run from a web browser.

256F has been making some progress to standardize this protocol as RAHP-D although in this particular case it make sense to implement in C.

[skot]

factories already have to plug in via USB to flash the firmware, so it would be pretty easy to run a test suite on the new bitaxe right after flashing.

[skot]

for situations like the TPS546 init where you want to test with what esp-miner is going to run, raw-mode could have commands to run those functions from esp-miner