clang-format: Improve wrapping of << operators.

Before:
  llvm::errs() << aaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
                     aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
                      aaaaaaaaaaaaaaaa) << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;

After:
  llvm::errs() << aaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
                      aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa,
                      aaaaaaaaaaaaaaaa)
               << aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa;

Also, cleanup and simplify the operator wrapping logic.

llvm-svn: 236960