merge stdlib tests (#9439)

tests/stdlib/txmltree.nim

@@ -1,27 +0,0 @@
-discard """
-  file: "txmltree.nim"
-  output: '''true
-true
-true
-true
-true
-'''
-"""
-
-import xmltree, strtabs
-
-var x = <>a(href="nim.de", newText("www.nim-test.de"))
-
-echo($x == "<a href=\"nim.de\">www.nim-test.de</a>")
-
-echo(newText("foo").innerText == "foo")
-echo(newEntity("bar").innerText == "bar")
-echo(newComment("baz").innerText == "")
-
-let y = newXmlTree("x", [
-  newText("foo"),
-  newXmlTree("y", [
-    newText("bar")
-  ])
-])
-echo(y.innerText == "foobar")