Add contextual help to Yay operations

[jdholtz]

This is a proposal to add #2780. I thought this would be a good addition to yay because it's exactly how pacman operates. Happy to discuss this further too.

Instead of yay -<op> --help printing the entire help message, it will now print a contextual help message based on the operation being performed.

The top-level help message shows available operations and global flags as before. It no longer shows operation-specific flags and pacman -S --help output. Like the pacman output, it shows that you can get operation-specific help by running yay -<op> --help.

The operation-specific help message shows the operation's flags and all pacman operation flags pass through to pacman.

Specifying -V and --version now always shows the version rather than having yay -V --help show the help message.

[Jguer]

I agree @jdholtz , let's merge it.

Questions unanswered for the future:

• How to ensure this is kept up to date
• Does pacman support localization of these and should we do the same

[jdholtz]

Questions unanswered for the future:

• How to ensure this is kept up to date
• Does pacman support localization of these and should we do the same

For keeping up to date, I don't think the process would necessarily because of this PR. The options still need to be updated in this help text, the man page, and the completions. Since that's so many places, I don't see a simple static check being feasible. That'd be a good option for an AI reviewer though.

For localization, yes pacman does support localization. Since we support localization in most (all?) text areas, we should support it for the help message too. I created #2944 to solve that.