[clang-format] Skip PP directives when determining brace kind (#69473)

Pull request #65409 changed the brace kind heuristic to not treat a
preprocessor if directive as a in statement, however, this caused some
regressions.

If the contents of a brace don't immediately determine the brace kind,
the heuristic will look at the characters immediately before and after
the closing brace to determine the brace type.

Unfortunately, if the closing brace was preceded by a preprocessor
directive, for example `#endif`, the preceding token was `endif`, seen
as just an identifier, so the braces were understood as a braced list.

This patch fixes this behaviour by skipping all preprocessor directives
when calculating brace types. Comments were already being skipped, so
now preprocessor lines are skipped alongside comments.

Fixes https://github.com/llvm/llvm-project/issues/68404