Allow to exclude certain target from nogo facts collection

[linzhp]

What type of PR is this?
Feature

What does this PR do? Why is it needed?
After #4268, nogo collects facts from all targets. So go_register_nogo's includes and excludes now overlap with the JSON config's only_files and exclude_files, which is to surppress nogo errors in certain files/targets. Meanwhile, collecting facts can be slow for very large Go packages for some analyzers, slower than compilation. To address the performance issue, this PR revert excludes to its previous behavior: stop nogo from collecting facts from certain packages, while making includes of go_register_nogo a no-op with a warning message, asking people to use the JSON config instead. So nogo will continue to collect facts from all targets, which is the safe default, except those in excludes.

Other notes for review
With this PR, users need to add a config like this to surppress issues in external repositories:

{
  "_base": {
    "exclude_files": {
      "^external/": "external repositories"
    }
  }
}

Or if all Go code they care about are under a specific directory, they can have:

{
  "_base": {
    "only_files": {
      "^src/": "All Go files in the current repo"
    }
  }
}

Alternatively, to be backward-compatible, we can add a flag or attribute like exclude_collect_facts, but adding that on top of excludes and exclude_files makes hard to remember which is which.

[linzhp]

With this, most repos no longer need the JSON config unless they want to exclude certain paths in the repo. @fmeum