fixes #23524; global variables cannot be analysed when injecting move (#23529)

fixes #23524

```nim
proc isAnalysableFieldAccess*(orig: PNode; owner: PSym): bool =
  ...
  result = n.kind == nkSym and n.sym.owner == owner and
    {sfGlobal, sfThread, sfCursor} * n.sym.flags == {} and
    (n.sym.kind != skParam or isSinkParam(n.sym))
```
In `isAnalysableFieldAccess`, globals, cursors are already rejected

lib/system.nim

@@ -158,9 +158,11 @@ when defined(nimHasEnsureMove):
     ## Ensures that `x` is moved to the new location, otherwise it gives
     ## an error at the compile time.
     runnableExamples:
-      var x = "Hello"
-      let y = ensureMove(x)
-      doAssert y == "Hello"
+      proc foo =
+        var x = "Hello"
+        let y = ensureMove(x)
+        doAssert y == "Hello"
+      foo()
     discard "implemented in injectdestructors"
 
 type