In preparation for go1.19 with generics I did some preliminary cleanup of the native overrides:

• I removed the old build tags, // +build. As it says in the go cmd docs that type of build tags were replaced with //go:build tags after go1.16. This will not affect reading files and // +build will still work.
• I formatted the imports (only caused single imports to inline).
• I went through the existing packages looking for tests which no longer fail or no longer exist in go1.19. I did not remove tests that required generics to function.
• I ran most of the packages without --short and added some overrides that were missing. There was a lot of issues in net/... and in runtime/... that I didn't fix because they were in the .std_test_pkg_exclusions and I didn't want to determine which packages in that, if any, we wanted to start supporting.
• For some of the tests which didn't specify why they were being skipped, I added a reason.