feat(cli)!: remove --json in favor of --format json

[davidpdrsn]

Removes the global --json flag in favor of using --format json. That way, there is only one way to specify the format.

@slarse and I think not having --format as a global flag is good since it might not make sense for all commands. Instead, the commands that support format should handle it specifically. This PR doesn't change that; --format is still global, but we'll look into it later. But to move in that direction, I added

#[derive(clap::Args)]
pub struct OutputFormatArg {
    #[clap(...)]
    pub format: OutputFormat,
}

which can be #[clap(flatten)]'ed into other arg structs later. Currently, it's just used in the top-level Args type.

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[krlvi]

This is fine. The agents are not using the --json flag but it is still useful for scripting.
Just dont forget to update the docs http://github.com/gitbutlerapp/gitbutler-docs

[slarse]

This is fine. The agents are not using the --json flag but it is still useful for scripting. Just dont forget to update the docs http://github.com/gitbutlerapp/gitbutler-docs

We shouldn't update the docs before release, should we? Updating docs should be automated but it should never happen before release unless we have an nightly docs subdomain or similar. Which we don't?

[davidpdrsn]

I've opened gitbutlerapp/gitbutler-docs#198 which we can merge when making a new release.