Consider activation frame for stack height metering (#2)

* Charge a base cost for calling a function

* Added regression test for empty functions

* Satisfy clippy

tests/fixtures/stack-height/global.wat

@@ -6,8 +6,8 @@
 
   (func $i32.add (export "i32.add") (param i32 i32) (result i32)
     get_local 0
-	get_local 1
-	i32.add
+	  get_local 1
+	  i32.add
   )
   (func (param $arg i32)
      (local $tmp i32)
@@ -15,7 +15,7 @@
      global.get 0
      i32.const 1
      i32.add
-	 tee_local $tmp
+	   tee_local $tmp
      global.set $counter
 
      get_local $tmp