Fix doxygen, split up CI jobs

[Donkie]

1. Fixed doxygen by adding a step where all src/ files are moved into the root folder. Adafruit's doxygen config is set to only look for code files in the root directory. This is bit of an ugly hack but it's the least invasive one. Alternatively, the src/ files should just be moved into the root like all other adafruit libraries. Alternatively, adafruit's doxygen config should be updated to also look for files in the src/ dir.
2. Updated files so doxygen doesn't complain anymore now that it actually can find the files.
3. Split the github CI jobs up abit, since they can and should be run independently. (Also, the doxygen fix moving the files breaks the examples for some reason so it's good to isolate that fix to just the doxygen job)

[ladyada]

wow thank you! didnt even notice this stopped doxygening!