Migrate to mason.nvim

[Allaman]

Before, one must ensure that required tools like LSPs, formatters, etc. are installed on the system. With this rework mason.nvim installs all required tools for you.

In order to migrate you should ...

• ensure that your system satisfies mason.nvim requirements
• ensure that all required languages/tool chains are available
• delete your formerly installed LSPs, linters, etc
• add the newly installed tools to your path (default is ~/.local/share/nvim/mason/bin)