[5.x] Add field actions modals

[jacksleight]

Summary

This PR builds upon #10352 and adds the ability to easily create confirmation/form modals from within the action run method, allowing you to prompt for user input before performing the rest of the action logic:

CleanShot.2024-09-24.at.18.33.14.mp4

The action for that looks like this:

Statamic.$actions.add('text-fieldtype', {
    title: 'Translate',
    run: async ({ value, update }) => {
        const { values: options, close } = await Statamic.$actions.modal({
            title: 'Translate',
            keepOpen: true,
            fields: {
                language: {
                    type: 'select',
                    display: 'Language',
                    instructions: 'Please select a language',
                    validate: 'required',
                    options: {
                        en: 'English',
                        es: 'Spanish',
                        fr: 'French',
                        de: 'German',
                        it: 'Italian',
                    }
                },
            }, 
        });
        const translated = await translationService({
            text: value,
            lang: options.language,
        });
        update(translated);
        close();
    },
});

The fields are passed to the backend to resolve a full blueprint for the form. The values are also passed to the backend for validation. The return data contains both pre-processed and raw values, as different use cases may need different types of values.

The keepOpen flag allows you to keep the modal and it's busy state visible after it's confirmed. This is useful if you then need to perform other long-running tasks and want to show some feedback to the user. Without it the modal just closes as normal on confirm.

Todo

• Figure out non-field (confirmation only) return data
• Figure out cancel return data (or throw?)
• Fix dirty state handling
• Should there be an automatic modal if fields are defined in the action?