fix 25667; Generic forward type confusion (#25737)

ref: #25667

drain deferred reification in a loop until there is no more work to do.
Could potentially evaluate the same deferred work more than once.

---------

Co-authored-by: Andreas Rumpf <araq4k@proton.me>

tests/objects/t25627.nim

@@ -68,3 +68,20 @@ block:
   let sized = Sized()
   doAssert sized.files.x == sizeof(Sized)
 
+block:
+  type
+    Generic[T] = object
+      t: T
+
+    WindowObj = object
+      svgCache: Generic[SVGSVGElement]
+
+    SVGSVGElement = Generic[SVGSVGElementObj]
+
+    SVGSVGElementObj = object
+
+  proc foo() =
+    let p: pointer = nil
+    discard cast[ptr WindowObj](p)
+
+  foo()