[Tolk] Get rid of ~tilda with mutate and self methods

This is a very big change.
If FunC has `.methods()` and `~methods()`, Tolk has only dot,
one and only way to call a `.method()`.
A method may mutate an object, or may not.
It's a behavioral and semantic difference from FunC.

- `cs.loadInt(32)` modifies a slice and returns an integer
- `b.storeInt(x, 32)` modifies a builder
- `b = b.storeInt()` also works, since it not only modifies, but returns
- chained methods also work, they return `self`
- everything works exactly as expected, similar to JS
- no runtime overhead, exactly same Fift instructions
- custom methods are created with ease
- tilda `~` does not exist in Tolk at all

tolk/pipe-generate-fif-output.cpp

@@ -39,10 +39,10 @@ bool SymValCodeFunc::does_need_codegen() const {
   if (flags & flagUsedAsNonCall) {
     return true;
   }
-  // when a function f() is just `return anotherF(...args)`, it doesn't need to be codegenerated at all,
-  // since all its usages are inlined
-  return !is_just_wrapper_for_another_f();
-  // in the future, we may want to implement a true AST inlining for `inline` functions also
+  // currently, there is no inlining, all functions are codegenerated
+  // (but actually, unused ones are later removed by Fift)
+  // in the future, we may want to implement a true AST inlining for "simple" functions
+  return true;
 }
 
 void SymValCodeFunc::set_code(CodeBlob* code) {