Fix/iterative update (#2206)

* use iterative algo to prevent exceeding recursion limit

* proper fixpoint

slither/solc_parsing/declarations/function.py

@@ -1106,11 +1106,13 @@ def _parse_unchecked_block(self, block: Dict, node: NodeSolc, scope):
         return node
 
     def _update_reachability(self, node: Node) -> None:
-        if node.is_reachable:
-            return
-        node.set_is_reachable(True)
-        for son in node.sons:
-            self._update_reachability(son)
+        worklist = [node]
+        while worklist:
+            current = worklist.pop()
+            # fix point
+            if not current.is_reachable:
+                current.set_is_reachable(True)
+                worklist.extend(current.sons)
 
     def _parse_cfg(self, cfg: Dict) -> None: