Provide config entity translation

Problem/Motivation

We need to provide the ability of translating config entities with Lingotek.

Proposed resolution

Replace ConfigTranslationController with our own Controller that extends that one with the Lingotek operations.
Expand LingotekConfigTranslationServiceInterface for providing the ability of uploading and requesting translations, and save that data into the language override configuration.

Remaining tasks

Review,
Commit.

User interface changes

The "Translate" tab of config entities have the Lingotek-related operations.

API changes

Expanded LingotekConfigTranslationServiceInterface with operations.

Data model changes

Added Lingotek config metadata into third-party settings.