CI: Run gofmt and clang-format automatically on pull requests

[dylanahsmith]

Problem

It is easy to forget to run go fmt or go generate to format the code. This results in these changes ending up in following PRs and even get squashed into them due to the PRs being squash merged.

Solution

Add a CI step that will fail if the code wasn't formatted and show the missing format changes.

[codecov]

Codecov Report

Merging #233 (f0f5bf9) into master (64149e7) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #233   +/-   ##
=======================================
  Coverage   95.86%   95.86%           
=======================================
  Files          17       17           
  Lines         580      580           
=======================================
  Hits          556      556           
  Misses         15       15           
  Partials        9        9           

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