display help instead of silently exiting on empty subcommands

[elseawhy]

Previously, running commands without arguments had inconsistent UX

Commands with optional arguments, like suggestions, mouse, editor would parse successfully, do nothing and silently exit:

Commands with required arguments, like perf, create-prompt-widget would print a help menu without any colour on the fonts and return a non-zero exit code (notice the red > on the screenshot):

What i did was adding arg_required_else_help = true to all subcommands that currently exit silently when no arguments are passed to it. I also updated the match arm in cli.rs to correctly handle ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand, now it should print help menu and exit successfully. Also added color = clap::ColorChoice::Always to FlylineArgs for consistency.

Here is what it looks like after:

[HalFrgrd]

Great, thank you!