fix(parser): Allow help and version command

[sebastiantoh]

Fixes #4392

Context

The help and version command are considered errors, though they are not "true" ones (I'm curious to know why they're considered errors to begin with 🤔 )

• clap/clap_builder/src/error/kind.rs

  Lines 259 to 277 in 1f71fd9

  	/// Not a true "error" as it means `--help` or similar was used.
  	/// The help message will be sent to `stdout`.
  	///
  	/// **Note**: If the help is displayed due to an error (such as missing subcommands) it will
  	/// be sent to `stderr` instead of `stdout`.
  	///
  	/// # Examples
  	///
  	/// ```rust
  	/// # #[cfg(feature = "help")] {
  	/// # use clap_builder as clap;
  	/// # use clap::{Command, Arg, error::ErrorKind};
  	/// let result = Command::new("prog")
  	/// .try_get_matches_from(vec!["prog", "--help"]);
  	/// assert!(result.is_err());
  	/// assert_eq!(result.unwrap_err().kind(), ErrorKind::DisplayHelp);
  	/// # }
  	/// ```
  	DisplayHelp,

• clap/clap_builder/src/error/kind.rs

  Lines 303 to 317 in 1f71fd9

  	/// Not a true "error" as it means `--version` or similar was used.
  	/// The message will be sent to `stdout`.
  	///
  	/// # Examples
  	///
  	/// ```rust
  	/// # use clap_builder as clap;
  	/// # use clap::{Command, Arg, error::ErrorKind};
  	/// let result = Command::new("prog")
  	/// .version("3.0")
  	/// .try_get_matches_from(vec!["prog", "--version"]);
  	/// assert!(result.is_err());
  	/// assert_eq!(result.unwrap_err().kind(), ErrorKind::DisplayVersion);
  	/// ```
  	DisplayVersion,

As a result, when ignore_errors is true, the output from the help and version commands are ignored.

Changes in this PR

This PR adds an explicit check so that only "true" errors are ignored

[epage]

I'm curious to know why they're considered errors to begin with thinking

We want to unwind the parsing and the application to a level that can decide how to handle it (e.g. exit the process). While this isn't a failure, it mirrors what the semantics of Result::Err

[sebastiantoh]

thanks for the review and explanations! i've made the requested changes