[clang-format] Correctly format goto labels followed by blocks

There doesn't seem to be an issue on GitHub.  But previously, a space
would be inserted before the goto colon in the code below.

    switch (x) {
    case 0:
    goto_0: {
      action();
      break;
    }
    }

Previously, the colon following a goto label would be annotated as
`TT_InheritanceColon`.  A goto label followed by an opening brace
wasn't recognized.  It is easy to add another line to have
`spaceRequiredBefore` function recognize the case, but I believed it
is more proper to avoid doing the same thing in `UnwrappedLineParser`
and `TokenAnnotator`.  So now the label colons would be labeled in
`UnwrappedLineParser`, and `spaceRequiredBefore` would rely on that.

Previously we had the type `TT_GotoLabelColon` intended for both goto
labels and case labels.  But since handling of goto labels and case
labels differ somewhat, I split it into separate types for goto and
case labels.

This patch doesn't change the behavior for case labels.  I added the
lines annotating case labels because they would previously be
mistakenly annotated as `TT_InheritanceColon` just like goto labels.
And since I added the annotations, the checks for the `case` and
`default` keywords in `spaceRequiredBefore` are not necessary anymore.

Reviewed By: MyDeveloperDay

Differential Revision: https://reviews.llvm.org/D148484