Changing the site wide language causes translated webforms to break.

Follow-up to #2854188: Translation issue

Problem/Motivation

Changing the site wide language causes a translated webform's elements to be lost.

There is no easy way to get a webform's element's render array to be translatable because it is almost impossible to define a config scheme for dozens of render elements within nested render array.
https://www.drupal.org/docs/8/api/configuration-api/configuration-schema...

The Webform module provides a WebformTranslationManager that extracts the translatable properties from a webform's element's render array.

Proposed resolution

OPTION 1: Detect when the site language changes and fix translated webform config.

OPTION 2: Track source language when a webform is created.

Remaining tasks

OPTION 1: Detect when the site language changes and fix translated webform config.

• Detect site language on install store as settings.
• Track website site language to current language
• Add conversion batch process to MskTranslationManager.
• Add warning to status report
• Add warning to translate tabs
• Add warning to change language form
• Write drush command
• Write tests

OPTION 2: Track source language when a webform is created.

• Add source_langcode to webform config
• Document the Source langcode
• Update WebformTranslationManager to use source_langcode for element definitions.
• Write update hook that sets the correctly source langcode for all existing configuration.
• Write tests

User interface changes

• Warning on Status Report
• Warning on Translate tab

API changes

• Webform module is tracking site language

Data model changes

None

Steps to Reproduce

• Install the Webform and Config Translation module
• Enable 'Spanish' ()
• Translate Contact form to Spanish
• Switch Default Language to 'Spanish'
• View Contact form and elements are missing.

Notes

Installing Webform on non-English (en) website

• Webform retains en langcode.
• English is still considered the (original)

New Webform created on a non-English website

• Webform's langcode is set to current language
• Current language is marked as original