Add "magic" mode for Go projects

[kjk]

Currently adding integration to a Go project requires writing a multi-step shell script.

Wouldn't it be nice if we could just do: fuzzit gomagic --org=kkowalczyk --fuzzing (or fuzzit gomagic --regression) and fuzzit just does the right thing?

(gomagic is just a placeholder name).

For most projects it would be possible to automate everything with heuristics.

It's not a replacement, just an addition (the old way would still work).

Roughly what this would do:

• for --fuzzing check api key is provided via FUZZIT_API_KEY or --auth option an exit with error message if not
• auto-detect fuzz targets by parsing code and looking for packages with gofuzz tag
• auto-detect corpus following some rules (e.g. it must be a "corpus" directory)
• install go-fuzz and build targets (with auto-naming of targets based on ${package}-${func}
• build fuzzing targets with clang
• create targets if not exist on the server
• upload jobs
• get git branch and commit from the repo
  etc.

The logic might grow to accommodate more complex scenarios but it could start with just simple scenarios like a single fuzz target.

It should log all the steps so that people understand what it does.

[yevgenypats]

Some steps here are easy to automate and some steps are much harder (to make them work in the general case). Let's put it here and see what we think after we gain more experience with go projects.

[yevgenypats]

moving this to internal trello. as well as some steps here are already done.