naga-cli: Support reading input from stdin

[rhysd]

Fixes #1700

Three changes are added to support reading from stdin:

• With argh crate, the INPUT argument cannot be optional. So this PR replaces argh with clap crate.
• The INPUT argument is now optional: naga [OPTIONS] [FILES...]
• Since a file path cannot be known when reading from stdin, so a new option --stdin-file-path <PATH> is added to notify the file path. This is the same way as eslint does.

[kvark]

With argh crate, the INPUT argument cannot be optional.

I don't think this reasoning is really sound. All it would take is to change this:

    /// the input file
    #[argh(positional)]
    input: String,

    /// the output file. If not specified, only validation will be performed
    #[argh(positional)]
    output: Vec<String>,

Into this:

    /// the input and output files
    #[argh(positional)]
    files: Vec<String>,

Would you be open to refactor the PR on top of argh?

[rhysd]

Would you be open to refactor the PR on top of argh?

That also makes sense to me. I will update this patch today.

[rhysd]

@kvark I updated this patch to keep argh dependency and force pushed the branch. Could you review the changes?

[kvark]

Nice!