fixes #24844; Invalid C codegen refc with generic types containing gc memory (#25160)

fixes #24844

it may not be used in other places except in `genTraverseProc`,
we have to generate a `typedesc` for this case, not a weak `typedec`

(cherry picked from commit a77d1cc6c1)

tests/refc/m24844.nim

@@ -0,0 +1,8 @@
+type
+  S*[T] = ref object of RootObj
+    k: string
+  A*[T] = ref object of S[T]
+
+proc p*[T](): S[T] = S[T]()
+proc u*() = discard A[int]()
+discard A[int]()

tests/refc/t24844.nim

@@ -0,0 +1,11 @@
+discard """
+  matrix: "--mm:refc; --mm:arc"
+  joinable: false
+"""
+
+import m24844
+
+u()
+
+type E = distinct int
+discard p[E]()