[Tolk] Completely rework stdlib: multiple files and renaming

- split stdlib.tolk into multiple files (tolk-stdlib/ folder)
  (the "core" common.tolk is auto-imported, the rest are
  needed to be explicitly imported like "@stdlib/tvm-dicts.tolk")
- all functions were renamed to long and clear names
- new naming is camelCase

tolk-tester/tests/invalid-symbol-1.tolk

@@ -4,11 +4,11 @@ fun main(x: int): int {
     } else {
         var y: slice = "20";
     }
-    ~dump(y);
+    debugPrint(y);
 }
 
 /**
 @compilation_should_fail
-@stderr ~dump(y);
+@stderr debugPrint(y);
 @stderr undefined symbol `y`
  */