[llvm-dwarfdump] Make commandline arguments consistent.

Currently, llvm-dwarfdump's help message has two issues.

1. Most long options are printed in `--long-option`, except for some section dumping options, e.g., `-apple-names`, `-debug-addr`.

2. Most options are printed with consistent indention, except for some section dumping options.

This patch helps resolve these two issues.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D79618