Automatic merge from submit-queue (batch tested with PRs 38049, 37823, 38000, 36646)

Test 0-length-arrays in fuzzing tests

While hacking on #37289 I noticed that our fuzzing tests test nil slices and slices of length 1, but not slices of length 0, meaning we aren't testing that 0-length slices get treated the same as nil in all the places we expect them to (and in particular, we aren't ensuring that comparisons always use api.Semantic.DeepEqual rather than reflect.DeepEqual). (Though in fact, changing the fuzzer didn't turn up any bugs, so maybe this effectively gets tested somewhere else...)

`fuzz.New().NilChance(.5).NumElements(0, 1)` means we end up generating `nil` 50% of the time, a length 0 array 25% of the time, and a length 1 array 25% of the time... maybe it should be `fuzz.New().NilChance(.33).NumElements(0, 1)` instead?

The gofuzz rebase is to pull in https://github.com/google/gofuzz/pull/20, and the other fix is just a drive-by.