staticcheck

[deepthi]

Fix #4639
Replace unused git pre-commit hook with staticcheck
Fix most of the errors thrown by staticcheck, ignore a few.

[dweitzman]

I haven't read through the whole diff. In general I would advocate for spitting up these kinds of changes into more, smaller, easier-to-review diffs unless the entire change has been written programmatically.

[deepthi]

I haven't read through the whole diff. In general I would advocate for spitting up these kinds of changes into more, smaller, easier-to-review diffs unless the entire change has been written programmatically.

Apologies for the huge diff. I didn't know when I started this how big it was going to be. The idea was to commit all the fixes along with the git hook so that things stay relatively clean after that. I have tried to keep each package in a separate commit to make it easier to review.