* plugins/none-ls: Use upstream builtins.json to list sources
This avoids the need to define sources in nixvim. We only need to define
a mapping from source names to packages.
This commit does not yet introduce sources for the newly available builtins
* plugin/none-ls: Enable all known sources in tests
* plugins/none-ls: Add all missing sources
This requires to pass the efmls-configs file to the derivation helpers,
if we try to import it from the test file directly it fails.
We then look into the types to find the available languages &
corresponding tools, to enable them all.
We then filter out the broken tools or the unpackaged tools, in order to
detect more easily the introduction of future tools.
