Add NoSuchCommand exception with suggestions for misspelled commands

[RC2215]

This PR adds suggestions to the "No such command" error message for misspelled commands, similar to how it's done for NoSuchOption.

As part of this update, a new exception was added - NoSuchCommand, along with slight formatting changes in NoSuchOption, to improve readability and ensure consistency with other errors.

Rejected idea: Adding a shared base exception or mixin for NoSuchOption and NoSuchCommand.

Fixes #3107.

Additional behavior changes

• The option possibilities are now calculated within the NoSuchOption exception.
• The normalized command name is now used in the NoSuchCommand error message.

Example based on the issue

import click


@click.group()
def cli():
    pass


@cli.command()
@click.option("--name", default="World")
def greet(name: str) -> None:
    click.echo(f"Hello, {name}")


if __name__ == "__main__":
    cli()

Before the change:

$ ./main.py greet --nme David
Usage: main.py greet [OPTIONS]
Try 'main.py greet --help' for help.

Error: No such option: --nme Did you mean --name?

$ ./main.py gret --name David
Usage: main.py [OPTIONS] COMMAND [ARGS]...
Try 'main.py --help' for help.

Error: No such command 'gret'.

After the change:

$ ./main.py greet --nme David
Usage: main.py greet [OPTIONS]
Try 'main.py greet --help' for help.

Error: No such option '--nme'. Did you mean '--name'?

$ ./main.py gret --name David
Usage: main.py [OPTIONS] COMMAND [ARGS]...
Try 'main.py --help' for help.

Error: No such command 'gret'. Did you mean 'greet'?

• Added unit tests for unknown and misspelled commands.