Support Yarn 2

The current implementation does not support Yarn 2, which is the current stable, so it is high time to migrate Yarn 1 to 2.

https://gitlab.com/gitlab-org/gitlab-build-images/-/blob/17d4e349aee2950a7f5ac14d99697beae02a5ba5/scripts/install-node#L13-21

TODO

• Avoid to use Yarn 1.21 !395 (merged) !396 (merged)
• Use only Yarn 1.22 (1.22.10)
• Change YARN_INSTALL_VERSION from Debian-based versioning to the upstream (Node.js') versioning in scripts/custom-docker-build, scripts/install-node, and scripts/install-www-gitlab-com at the same time as well as using npm repo instead of (Yarn's official) ppa repo !397 (merged)

State from the upstream

Packages provided by the official yarn ppa

$ apt-cache madison yarn | head
      yarn |   1.22.5-1 | https://dl.yarnpkg.com/debian stable/main amd64 Packages
      yarn |   1.22.5-1 | https://dl.yarnpkg.com/debian stable/main all Packages
      yarn |   1.22.4-1 | https://dl.yarnpkg.com/debian stable/main amd64 Packages
      yarn |   1.22.4-1 | https://dl.yarnpkg.com/debian stable/main all Packages
      yarn |   1.22.1-1 | https://dl.yarnpkg.com/debian stable/main amd64 Packages
      yarn |   1.22.1-1 | https://dl.yarnpkg.com/debian stable/main all Packages
      yarn |   1.22.0-1 | https://dl.yarnpkg.com/debian stable/main amd64 Packages
      yarn |   1.22.0-1 | https://dl.yarnpkg.com/debian stable/main all Packages
      yarn |   1.21.1-1 | https://dl.yarnpkg.com/debian stable/main amd64 Packages
      yarn |   1.21.1-1 | https://dl.yarnpkg.com/debian stable/main all Packages

No more packages for Yarn 2 on their ppa repo at dl.yarnpkg.com.

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Notice from the upstream

https://classic.yarnpkg.com/en/docs/install

Installation

These instructions only cover Yarn versions prior to 2.0. Those versions entered maintenance mode in January 2020 and will eventually reach their end-of-life in terms of support. Please see the main website for the most up-to-date documentation: yarnpkg.com/getting-started/migration.

The latest Yarn version is: v3.0.0-rc2