Finish knip setup

[mdirolf]

I started setting up knip and it did manage to find a couple of files that were completely dead. It seems possible that removing unused exports might cascade to some more code elimination. We should also try to get this into CI once we have it "passing" against the current codebase.

It can be run with yarn knip. There are some dependency issues listed many of which I'm willing to believe should be changed, though some seem like false alerts we should sort (the lingui stuff, for example, is actually used I think). The main false alert I'd like to figure out, though, is doGlicko which is listed in unused exports but I know is imported in function/src/index.ts (which I thought I successfully added to the list of entrypoints.