[docs][llvm-symbolizer] Improve llvm-symbolizer documentation
As detailed in https://bugs.llvm.org/show_bug.cgi?id=42253, there were a
number of issues in the llvm-symbolizer documentation. This patch fixes
- Adding [addresses...] to the synopsis, and matching the formatting of other tools.
- Rewriting the description to fix grammar issues and mention other usage options.
- Rewriting the examples to be easier to read.
- Re-ordering the options into alphabetical order.
- Improving the text of some of the option descriptions, and adding some examples to individual options.
- Splitting the Mach-O options into a separate section of the document.
- Standardizing on double dashes for long options throughout the file.
- Adding a reference to the llvm-addr2line document.
Reviewed by: mtrent, ikudrin
Differential Revision: https://reviews.llvm.org/D63651