Auto merge of #10753 - epage:clap32-deprecated, r=weihanglo

Auto merge of #10753 - epage:clap32-deprecated, r=weihanglo

chore: Upgrade to clap 3.2

I decided to use cargo as a test case for upgrading to clap 3.2 prior to release.  From the builder API's perspective, a lot has change.  While the changelog summarizes it, the release announcement is still pending.  In short, the API is now typed.  You declare what type an `Arg` is and access it by that type.  flags (both `is_present` and `occurrences_of`) are also now specified through `ArgAction` and the result gets stored like any other arg value.  I made a `ArgMatchesExt::flag` and `command_prelude::flag` functions to make working with these easier.

Now that clap exposes non-panicking variants of its functions, I switched from a "look before you leap" approach with `is_arg_valid` to a "better to ask forgiveness than permission" with checking the error variant.  I decided to just make a convenience to swallow that error type.  Not a fan of how loose things are but I think this will just be something we iterate on over time.