Automatic deref for everything but pointers in asm/emit (#8891)

Fixes #7249

tests/js/t7249.nim

@@ -0,0 +1,21 @@
+discard """
+  output: '''
+a -> 2
+a <- 2
+'''
+"""
+
+import jsffi
+
+var a = JsAssoc[cstring, int]{a: 2}
+
+for z, b in a:
+  echo z, " -> ", b
+
+proc f =
+  var a = JsAssoc[cstring, int]{a: 2}
+
+  for z, b in a:
+    echo z, " <- ", b
+
+f()

tests/js/tmangle.nim

@@ -27,10 +27,10 @@ block:
   var global = T(a: 11, b: "foo")
   proc test(): bool =
     var obj = T(a: 11, b: "foo")
-    {. emit: [result, " = (", obj.addr[], "[0].a == 11);"] .}
-    {. emit: [result, " = ", result, " && (", obj.addr[], "[0].b == \"foo\");"] .}
-    {. emit: [result, " = ", result, " && (", global, "[0].a == 11);"] .}
-    {. emit: [result, " = ", result, " && (", global, "[0].b == \"foo\");"] .}
+    {. emit: [result, " = (", obj.addr[], ".a == 11);"] .}
+    {. emit: [result, " = ", result, " && (", obj.addr[], ".b == \"foo\");"] .}
+    {. emit: [result, " = ", result, " && (", global, ".a == 11);"] .}
+    {. emit: [result, " = ", result, " && (", global, ".b == \"foo\");"] .}
   echo test()
 
 # Test addr of field:

tests/js/tstringitems.nim

@@ -45,7 +45,7 @@ block: # Test compile-time binary data generation, invalid unicode
 block: # Test unicode strings
   const constStr = "Привет!"
   var jsStr : cstring
-  {.emit: """`jsStr`[0] = "Привет!";""".}
+  {.emit: """`jsStr` = "Привет!";""".}
 
   doAssert($jsStr == constStr)
   var runtimeStr = "При"