[All] Re-enable indentation based folding

[deathaxe]

This commit re-enables indentation based folding for all syntaxes which have not yet been covered by other PRs.

Syntax based folding doesn't cover all possible use cases and therefore shouldn't be the only one.

Related with #3568, #3601

[BenjaminSchaaf]

I don't think this is generally a good idea as with syntaxes like D, rust and especially lisp I'd expect most users of code folding to prefer only scope-based folding.

[deathaxe]

Maybe Lisp is simple enough to restrict it to syntax based folding, but several other syntaxes

1. don't provide consistent meta.[group|block|...] scopes under all circumstances to distinguish fold regions reliably (e.g. expressions like ( code ( code )) ).

2. don't provide rules to fold statements like switch case

In D the case blocks are currently not foldable as those rely on indentation folding.

switch (a) {

   case 0:
      // not foldable code
      break;

   case 1:
      // not foldablecode
      break;
}

IMHO, both indentation strategies live good enough next to each other to be enabled at the same time by default.