[llvm-nm] Switch command line parsing from llvm::cl to OptTable

[llvm-nm] Switch command line parsing from llvm::cl to OptTable

Part of https://lists.llvm.org/pipermail/llvm-dev/2021-July/151622.html
"Binary utilities: switch command line parsing from llvm::cl to OptTable"

Users should generally observe no difference as long as they only use intended
option forms. Behavior changes:

* `-t=d` is removed. Use `-t d` instead.
* `--demangle=0` cannot be used. Omit the option or use `--no-demangle` instead.
* `--help-list` is removed. This is a `cl::` specific option.

Note:

* `-t` diagnostic gets improved.
* This patch avoids cl::opt collision if we decide to support multiplexing for binary utilities
* One-dash long options are still supported.
* The `-s` collision (`-s segment section` for Mach-O) is unfortunate. `-s` means `--print-armap` in GNU nm.
* This patch removes the last `cl::multi_val` use case from the `llvm/lib/Support/CommandLine.cpp` library

`-M` (`--print-armap`), `-U` (`--defined-only`), and `-W` (`--no-weak`)
are now deprecated. They could conflict with future GNU nm options.
(--print-armap has an existing alias -s, so GNU will unlikely add a new one.
--no-weak (not in GNU nm) is rarely used anyway.)

`--just-symbol-name` is now deprecated in favor of
`--format=just-symbols` and `-j`.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D105330