Upgrade to clap v4

[nezuo]

I need clap v4 for my planned changes for #715 because it has a new feature called argument relations. I can use the feature to stop users from using project and output flags at the same time.

New output

Clap changes the output from v3 to v4. Here's what the difference looks like:

Clap v3

Clap v4

Notice the lack of colors, the new casing, the bold, and the underlines.

Changes

• I no longer display the author since rojo no longer has a sole author.
• For whatever reason, clap v4 does not allow a default of "" for paths. Instead, I use the actual paths like default.project.json. Now it shows up in the help output:
  

[Dekkonot]

Personally, I don't care about the formatting changes and the loss of colors is... tragic, but acceptable in my opinion. Hesitantly, I think this is fine with me.

What does the alternative for not upgrading look like? I know it wouldn't display as exclusive in help but is that necessarily a deal breaker? We could always just raise an error if both fields are filled in.

[nezuo]

Here's a few screenshots of what the output looks like with argument relations for reference:

[Dekkonot]

That's kind of a funky syntax. I know it's not something you can control, but I don't like it. That said, it's not a deal breaker because most people will probably just be memorizing how to use a command anyway.

Would like to hear @Kampfkarren's and @kennethloeffler's inputs on this too, since it's a bit more of a design choice than normal and I want to make sure that multiple eyes okay it.

[kennethloeffler]

Notice the lack of colors

taking away my colors? Everything is already gray enough 😭

Jokes aside... I agree with dekkonot, the changes to formatting/colors aren't a big problem, but it may be a smarter engineering decision to hold off on upgrading until we have a more compelling reason to do it (like maybe another mutually exclusive set of flags, or anywhere else we could use other new clap features)

[nezuo]

I've decided to close this PR and implement the plugin flag without clap v4: #735.

The removal of colors is a somewhat controversial change, and although the output in #735 isn't amazing, clap v4's output isn't either.

If clap ever decides to support colors again, it's easy to upgrade.