fixes #24770; Thread local not registed as GC root when =destroy exists (#24776)

fixes #24770

e.g. `seq[(ObjectWithDestructors, string)]`/ For refc, a seq with
elements that have destructors will have `hasAsgn` flags. The flag is
the criteria whether a seq is thought as `containsGarbageCollectedRef`.
i.e. whether to `registerTraverseProc` for the type.
The culprit seems to be that `searchTypeForAux` doesn't consider the
element type of sequence, even it contains a string that should belong
to `GarbageCollectedRef`.

With this PR:

It now generates

```
nimRegisterThreadLocalMarker(TM__mSF73dT1lSI7DG58StKHLQ_5);
```

in refc

Author: ringabout

compiler/ccgstmts.nim

@@ -18,7 +18,7 @@ proc registerTraverseProc(p: BProc, v: PSym) =
   var traverseProc = ""
   if p.config.selectedGC in {gcMarkAndSweep, gcHooks, gcRefc} and
       optOwnedRefs notin p.config.globalOptions and
-      containsGarbageCollectedRef(v.loc.t):
+      containsManagedMemory(v.loc.t):
     # we register a specialized marked proc here; this has the advantage
     # that it works out of the box for thread local storage then :-)
     traverseProc = genTraverseProcForGlobal(p.module, v, v.info)