LibWasm: Start implementing a naive bytecode interpreter

As the parser now flattens out the instructions and inserts synthetic
nesting/structured instructions where needed, we can treat the whole
thing as a simple parsed bytecode stream.
This currently knows how to execute the following instructions:
- unreachable
- nop
- local.get
- local.set
- {i,f}{32,64}.const
- block
- loop
- if/else
- branch / branch_if
- i32_add
- i32_and/or/xor
- i32_ne

This also extends the 'wasm' utility to optionally execute the first
function in the module with optionally user-supplied arguments.

Userland/Libraries/LibWasm/AbstractMachine/Configuration.h

@@ -24,7 +24,7 @@ public:
     {
         m_current_frame = frame.ptr();
         m_stack.push(move(frame));
-        m_stack.push(make<Label>(m_current_frame->expression().instructions().size() - 1));
+        m_stack.push(make<Label>(m_current_frame->arity(), m_current_frame->expression().instructions().size() - 1));
     }
     auto& frame() const { return m_current_frame; }
     auto& frame() { return m_current_frame; }
@@ -34,10 +34,14 @@ public:
     auto& depth() { return m_depth; }
     auto& stack() const { return m_stack; }
     auto& stack() { return m_stack; }
+    auto& store() const { return m_store; }
+    auto& store() { return m_store; }
 
     Result call(FunctionAddress, Vector<Value> arguments);
     Result execute();
 
+    void dump_stack();
+
 private:
     Store& m_store;
     Frame* m_current_frame { nullptr };