Optimize lent in JS [backport:1.6] (#19393)

* Optimize lent in JS [backport:1.6]

* addr on lent doesn't work anymore, don't use it

* use unsafeAddr  in test again for older versions

tests/js/tlent.nim

@@ -0,0 +1,33 @@
+discard """
+  output: '''
+hmm
+100
+hmm
+100
+'''
+"""
+
+# #16800
+
+type A = object
+  b: int
+var t = A(b: 100)
+block:
+  proc getValues: lent int =
+    echo "hmm"
+    result = t.b
+  echo getValues()
+block:
+  proc getValues: lent int =
+    echo "hmm"
+    t.b
+  echo getValues()
+
+when false: # still an issue, #16908
+  template main =
+    iterator fn[T](a:T): lent T = yield a
+    let a = @[10]
+    for b in fn(a): echo b
+
+  static: main()
+  main()