patch 8.2.4257: Vim9: finding global function without g: prefix inconsistent

Problem:    Vim9: finding global function without g: prefix but not finding
            global variable is inconsistent.
Solution:   Require using g: for a global function.  Change the vim9.vim
            script into a Vim9 script with exports.  Fix that import in legacy
            script does not work.
diff --git a/src/testdir/test_glob2regpat.vim b/src/testdir/test_glob2regpat.vim
index 824693d..17ae3fc 100644
--- a/src/testdir/test_glob2regpat.vim
+++ b/src/testdir/test_glob2regpat.vim
@@ -1,11 +1,11 @@
 " Test glob2regpat()
 
-source vim9.vim
+import './vim9.vim' as v9
 
 func Test_glob2regpat_invalid()
   if has('float')
     call assert_equal('^1\.33$', glob2regpat(1.33))
-    call CheckDefAndScriptFailure(['echo glob2regpat(1.2)'], ['E1013: Argument 1: type mismatch, expected string but got float', 'E1174: String required for argument 1'])
+    call v9.CheckDefAndScriptFailure(['echo glob2regpat(1.2)'], ['E1013: Argument 1: type mismatch, expected string but got float', 'E1174: String required for argument 1'])
   endif
   call assert_fails('call glob2regpat("}")', 'E219:')
   call assert_fails('call glob2regpat("{")', 'E220:')