Restore the Nim's 0.14 proper handling of generic aliases

A more efficient implementation is possible by restoring the old
lifting ot tyGenericInvocation to tyGenericInst in liftTypeParam,
but this fix will suffice for now.

fixes #5087
fixes #5602
fixes #5641
fixes #5570

tests/generics/t5602_inheritence.nim

@@ -0,0 +1,18 @@
+discard """
+  output: "seq[float]\n0"
+"""
+
+# https://github.com/nim-lang/Nim/issues/5602
+
+import typetraits
+
+type
+  Foo[T] = object of RootObj
+  Bar[T] = object of Foo[seq[T]]
+
+proc p[T](f: Foo[T]): T =
+  echo T.name
+
+var s: Bar[float]
+echo p(s).len # the bug was: p(s) should return seq[float], but returns float instead
+