Cleans up a whole bunch of things I wanted to get out of the door
right away:
* depot internal references to //third_party/nixery have been replaced
with //tools/nixery
* cleaned up files from Github
* fixed SPDX & Copyright headers
* code formatting and inclusion in //tools/depotfmt checks
Change-Id: Iea79f0fdf3aa04f71741d4f4032f88605ae415bb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5486
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>
ALl the ones except for build-image.nix are considered trivial. On the
latter, nixfmt makes some useful changes but by-and-large it is not
ready for that code yet.
Executes the previously added mdBook on the previously added book
source to yield a directory that can be served by Nixery on its index
page.
This is one of those 'I <3 Nix' things due to how easy it is to do.
