[8.x] Images updates to 21.7.0 and Composer 2

Docker

• Added Composer 2.
• Updated images to 21.7.0 and PHP 7.4.
• Updated Xdebug flag value to use true for the new Docker images. Upstream #251

CI and workflow

• Updated behat-screenshot to the latest version.
• Updated behat-steps to use the new namespace. (#633)
• Updated behat-format-progress-fail to the latest version.
• Removed obsolete AMAZEEIO_ variables in favour of MARIADB_.
• Removed port check from builds on Linux.
• Added support for DATABASE_SSH_FINGERPRINT in CI.
• Fixed parameter parsing within deployment notification script.

Back-end

• Added running of post_update hooks on core module install.

Front-end

• Updated FE development packages to the latest versions.
• Added ahoy fei command to install FE packages.

Integrations

• Fixed environment detection in Lagoon.
• Updated Lagoon config to use correct configuration for routes for production and development environments.
• Fixed Lagoon deployment not using production branch variable.
• Fixed Lagoon private registry password variable name.
• Fixed Lagoon dotfiles were not copied into container.
• Fixed DB being sanitised in Acquia.

Documentation

• Updated command descriptions and run all tests.