[llvm] [llvm-support][llvm-profdata] Use cl::Subcommand to organize show options. And look up in top-level as a fallback if a special subcommand doesn't have an option. (PR #71328)

[David Li via llvm-commits]

https://github.com/david-xl commented:

Since the options are now attached to ShowSubCommand, there is no longer the need to use show_options namespace.

https://github.com/llvm/llvm-project/pull/71328