Add a service alias for ConfigurableLanguageManagerInterface

Problem/Motivation

Discovered in #3578361: Autowire all forms

Drupal\language\ConfigurableLanguageManagerInterface has a primary implementation in Drupal\language\ConfigurableLanguageManager, so we should add an alias so it can be autowired.

Steps to reproduce

Proposed resolution

Add the alias from ConfigurableLanguageManagerInterface to language_manager.
Remove any manual attributes of #[Autowire(service: 'language_manager')]

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet